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DTICELECTE_OV 1 4 1995
F
NASA Contractor Report 159304¢4
" s for
Graphite Fibers
F.S. Galasso _ _
D.A. Scola
R.D. Veltri
UNITEDTECHNOLOGIES RESEARCH CENTEREast Hartford, CT 06108
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CONTRACT NAS1-14346AUGUST 1980
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NASA CR-159304
Coatings for Graphite Fibers
F. S. Galasso
D. A. Scola
R. D. Veltr£
FIHALREPORT
Contract NA$I-14346
August 1980
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Coatings for Graphite Fibers
TABLE OF CONTENTS
Sb_1RY ................................... !
1.0 INTRODUCTIOE .............................. 2
].i Background ........................... 2
1.2 Objectives .......................... 2
1.3 Summary of Results fro_ Previous Studies ............ 2
2.0 EXPERI_IERTAL PROCEDURES ....................... 4
2.1 Coating Apparatus and Procedures ................ 4
2.1.1 Continuous CVD SiC Apparatus ............... 4
2.1.2 Static CVD Si_N_ Coating Apparatus 42.1.3 Static CVD B_Coatlng Apparatus ............. 5
2.1.4 Organo-Stlicone Coattng Apparatus for Continuous
Process Studies ..................... 52.2 Fiber Test Procedures ..................... 6
2.2.1 Electrical Resistance Measurements ............ 6
2.2.2 ArcJ_ug Tests ....................... 6
2.2.3 Ultimate Tensile Strength Measurements .......... 6
2.2.3.1 Single Filament Tests .............. 6
2.2.3.2 Yarn Tests ................... 7
2.2.4 Coating ThlclmessMeuuremenca .............. 7
2.2.5 X-ray D1ffractlonAnalysls ................ 7
2.3 Composite Test Procedures .................... 8
2.3.1 Epoxy Resin Flexural Strength Measurements ........ 8
2.3.2 Pabrleatlon of Graphlte/Epoxy Prepreg Tape ........ 8
2.3.3 Fabrication of Graphlte/Epoxy Composites ......... 82.3.4 Flexural Property Keasurement .............. 9
2.3.5 Shear Strength Measurement ............... 9
3.0 DISCUSSIOX A._TDRESULTS ........................ 10
3.1 CVD SiC Coating Approach ................... i0
3.2 C_ SI3Y h Coating Approach ................... 12
3.3 C_ BY Coating Approach .................... 15
3.3.1 CVD BN Cellon 6000 Graphite Yarn ............. 16
3.4 Evaluation of CVD SiC Coated Graphlte Yarns in Composites .... 17
3.4.1 Summary of Previous Studles wlth _ SiC Coated
Graphlee Yarn Composites ................. 17
3.4.2 CVV 51C Coated HMS Graphite Yarn/Epoxy Composites .... 18
3.5
3.6
3.4.3 CVD SiC Coated Celion Graphite Yarn/Epoxy Composite8 .... 18
3.4.4 CVD SIC Coated T-300 Graphite Yarn/Epoxy Composltes .... 19
3.4.5 CVD SiC Coated Cellon 12000 Graphlte Yarn/Composltes .... 19
3.4.6 Summary of CVD SiC Coated Graphite Yarn/Epoxy
Composite Data ....................... 20
3.4.7 Composites Delivered to NASA ................ 20
CVD Si3N _ Coated 14145 Graphite Yarn/Epoxy Composites ........ 2DDiscussion of Organo-Sillcon Approach to Develop Coated
Graphite Fibers with High Electrical Resistance .......... 213.6.1 Results of Previous Studies - Static Test Runs ...... 21
3.6.2 Results of Previous Coaclns Experiments in a Continuous
Reactor ......................... 22
3.6.3 Studies Using Modified Continuous Coating Reactor ..... 22
3.6.3.1 Ethyl Sillcate Coating Scudles .......... 22
3.6.3.1.1 Fiber Properties ............ 23
3.6.3.2 Glass Resin 100 Coating Studies .......... 24
3.6.3.2.1 Fiber Properties ............ 24
3.6.3.3 Glass Resin 650 Coating Studies .......... 24
3.6.3.3.1 Fiber Properties ............ 25
3.6.3.4 Trl-n-butylborate Coating Studies ......... 25
3.6.4 Evaluatlon of Sillca-llke Coated Cellon 6000 graphite
Fibers in Epoxy Composltes ................. 26
3.6.4.1 Composite Properties ............... 26
3.6.5 Conclusions o_ Organo-Silicone Coating Studies ....... 26
4.0 GENERAL CONCLUSIOIqS ..........................
5.0 REFERENCES ...............................
TABLES I - 39 ................................
27
29
3O
FIGURES 1 - 31
CoatinRs for Graphite Flbers
SU_4ARY
Several approaches for applying high resistance coatings continuously to
graphite yarn were investigated. Two of the most promising approaches involved
(1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber
followed by oxidation and (2) drawlng the graphite yarn through an organo-
silicone solution followed by heat treatments. In both methodsp coated fibers
were obtained_tch exh_bited increased electrical resistances over untreated
fibers and which were not degraded. This work was conducted in a previous program.
In this program, the continuous CVD SiC coating process used on HTS fiber
was extended to the coating of HM5, Cellon 6000, Cellon 12000 and _-300 graphite
fiber. Electrleal reslstances three orders of .mgnltude greater than the un-
coated fiber were measured wlth no significant degradation of the fiber strengths.
Graphite fibers coated with CVD SI3N _ and BN had resistances greater than 10 6
ohs/cm.
Lower pyrolysls temperatures were used In preparing the sillca-11ke coatings
also resulting in resistances as high as three orders of magnitude higher than
the uncoated fiber. The epoxy matrix composites prepared using these coated
fibers had low shear strengths indicating the coatlngs were weak.
"Use of commercial products or names of manufacturers in this report does not
constitute official endorsement of such products or manufacturers, either ex-
pressed or implled, by the Eatlonal Aeronautics and 5pace Administration."
I.O IN'_.ODUCIIO_
1.1 Background
Over the pa_t several years, graphite fibers have been used to produce low
density high strength composites for many aerospace structures. _he interest
in these composites has been growing steadily especially for use in aircraft
structures. Because of this growing interest, it became of concern to both com-
posite users and manufacturers when it was announced that the release of carbon
fibers from composlCes due to fire or exploslons could have serious effects on
eleccrical and _lectronlc equlpment (Refs. 1,2).
1.2 Objectives
In order to solve this problem, ];ASA looked st several approaches to either
pcevent the release of fibers or to make the fibers nonco_ductive so they would
not short c_rcuiC electrical equipment. A summary of these approaches was dls-
cussed at a I_.a_SAworkshop in _amptonp VA on }Larch 23-24, 1978 (Ref. 3).
1.3 Summary of Results froa Previous $tudl_s
The approach taken on this NASA program to solve the fiber conductivity
problem was to coat the graphite fibers with a layer which would increase the
resistance of the fiber, llerculea tiTS graphite fibers were selected for use in
the development of electrically resistanL _cqtings because of the wide range of
program._ for _-h_ch this fiber was being used. A preliminary study was first con-
ducted on draw£n$ graphite fiber through glass, dipping the fibers in eollogdal
silica, dra_ing fiber through organc-siltcone8 and chemical vapor depositing
(CUD) coatLu_s of SiC and B or B alloys. This was followed by a more detailed
study of the moec promLsing methods which were the CVD SIC coating and organo-
silicone approaches using graphite f4bers. This work was reported Ln NASA CI-
159078 (Ref. 4).
In the CVI) S£C co_ing s_udles, it was shown that tiTS graphite fibers could
be coated continuously _rtthouC degrading the fibers. The electrlcal resistance
yam highest (1000 ohas compared co 2 ohms for the untreated yarn) when a =eactor_e_peracure o£ 1398 K was used, a drawing race of 30 ca/aim and an £n-1/ne oxi-
daC£on temperature of 773 K. For the organo-sillcone method of coating HTS
graphlCe fiber, the best conditions wets as follows: concenCretion o£ echyl-
silicate 2,$ wc Z, drmrln s rate 0.91 m/rain end pyrolysis eemperature of 1093-
1173Kin a nitrogen ataosphere. The resistance of these fibers was 1_ oham va
2 ohms for _he _ntreated fiber m_d no degradation of the fiber yam obse.'_d.
This progrm reported herein extended the CVDSiC eoattnS studies to HNS.Celton 6000. Celion 120008BdT-300 sraphite fibers, l_e orgm_-sllieome coating
approach was further studied ustn8 the Celion 6000 graphite fiber as the rein-
forcenent and new costing materials were investigated. Additional 8tudie8 were
initiated on C_D silicom nitride and boron nitride coated 8raphite fibers. C_
el!Icon nltrlde and boron nltrlde have very high electrlcal resistances, but
presented some problems In deposition since It had to be done at very lov pres-
sures. Therefore. the objective of this part of the prosramwas to evaluate the
CVD silicon nitride and boron nttride processes for formins coattnK8 on graphite
fiber to Increase the resistance of the fiber vhtle not decreasing its strensth.
2.0 EXPERINEb'TAL PROCEDURES
2.1 Coatln& Apparatus and Procedures
2.1.1 Continuous CVD SiC Apparatus
Continuous deposition of the SiC CVI) coating of the 8rsphlte fibers was
_arried out in the apparatus shown in Fig. i. Axgon 8e_ seals at both ends of
the reactor kept the reactant gases within the chamber and mlni_tzed the intro-
duction of outside air into the hot zone. An rf induction coil was used to heat
the graphite susceptor which was placed within a double walled water cooled
silica chamber. The inner graphite susceptor was separated from the silica
walls with aluminum oxide spacers. Am in-line oxidation furnace was placed be-
tween the exit part of the reactor and the take-up spool.
The reactant gases were introduced into the reactor after the graphite
yarn had been brought to the desired temperature. The reactant gas flow rates
were nominally 0.015 Z/rain of methyldichlorostlane, 0.110 £/_n of hydropn
and 0.110 t/_n of _thane. The uthyldichlorostlane vapoz needed for the SiC
deposition process was obtained from a Liquid evaporator. A schematic of this
evaporator is shown in ¥i8. 2. The constant _rature of the water Jacket
_osether wlCh _he pressure vithin the supply tank was maeured so that calcu-lations could be made to deteraine the amount of aethyldlchloroeilane which was
being introduced into the reactor during deposition experlments.
2.1.2 Static CVD S£3N_ Coating Apparatus
Two apparatus were used for the static chemical vapor depo_ltion of silicon
nitride. In one, _xcures of silicon tetrafluorlde and ammonia were Ineroduced
Into a large cyllndrlcal hot reaction chmabez. The graphite fiber _o be coated
was suspended within this chamber, A photograph of r_e graphite red,stance £ur-nace used in the initial experiments is shown in Fig. 3 and a schematic drawing
of this apparatus is shown in Fig. 4. The reactant gases were brought into the
furnace separately and mixed immediately before passing over the hanging graphite
yarn. The pumping system capacity was adjusted to remove the exhaust gases at
such a rate that there was always a supply of fresh reactant gas around the
grsphlte yarn.
Deposition temperatures of from 1673 to 1873 K have been used ¢o for_ C_D
S£3N _ in this apparatus. For this progral an initial deposition telperature of1723 K was chosen since preliminary UTRC research on coating graphite yarn shoved
that this temperature yielded a good coating without visible degradation of the
graphite fibers. Si_lar _.asonin8 was used to choose the mole ratios of reac-
tant gas and the pressure _r_thin the reactor co conduct a series of experl_nts
in _lch graphite fiber was statlcally coated.
Anorhar apparatus consisted of a double walled water cooled slllca Jacket
with appropriate glass ftttinp for vacuum md 10_ pressure operation. A graphite
cyl/_der vM placed within the water cooled silica tube 8_d rf /nductton heating
was used to brinj _lts Kraphite cylinder up to the desired deposttAon tenpereture.
the sraphtte yarn to be costed was suspended in the center of the heated tube and
provisions vere made for the _nCroductton and exhaust of the Kases. In this
apparatus a 35 kW rf £nductlon unit yes used to heat the graphite cyllnder in
which the graphite yarn yes suspended. In Fi$. 5 Is shown a photosraph of th£s
epparatus.
2.1._ Static CVD BN Coatlng Apparatus
The static chenIcal vapor depoeltlon of boron nltrlde was carried out in
the sam large cylindrical hot reaction chamber that was prewlously described
for the $13N 4 experiments and shown in Fig. 3. In this case BF 3 and NH 3 were
used as the reactant gases.
2.1.4 Org_no-Slllcone CoatlnE aratus ._ ...................... _-
A deecrlptlon of static ezperLsents and results were given in NASA Con-
tractor Report 159078 (Ref. 4). TWo apparatus designs were used for continuous
fiber coetlng. The first contSnuous fiber coatlnK _paratus yes also described
in the referenced report.
The second apparatus vu a _odlflcatlon of the flrst deslgn, to pro-
vlde for several i_provemnts In operat£on and control of the coetlns pz_c_s.
These lnprovements include separation of the dryin8 and hydrolysis chanbex into
two separate chambers, (1) to provide improved dryinK of the fiber after solution
tmpzeKnstion of the graphite yarn, (2) a separate hydrolysis chamber to preventcontamination of r3e coatin_ solution by water, and for increased hydrolys_s tem-
peratures. In the previous de8tEn , a portion of the coating solution was under
the dryiu$ and hydrolysis chmnber, causin$ sons conca=Lnation of the solution by
water. Additional improvements were made in the drying chamber after hydrolysis,
an increased number of temperature sensors for temperature control, and Teflon
pulleys to prevent yarn crossover.
Coating 8Cudles of two systems [roa _he statlc test coating results and
from the first continuous coating results were contl_ued in tSe _odifled con-
tlnuous coating apparatus shown in Flg. 6. These were sllleone resin GE,
SR-355 and prepoly_er ethyl silicate (ES), the Rans_n & Randolph Co, R&R
slllcate binder #18. In addltlon, O_ens-llllnols glas_ resins 100 and 650
and tr_-n-butylborate were also investigated using the modified contlnuous
process equipment.
2.2 Fiber Test Procedures
2.2.1 Electrical Resistance Dfeasurements
A techrLtque for obtaining the relative, but only approximatej resistance
of one coated yarn ccapared to another involved laying out the coated fiber on
an insulator. Two copper blocks 2.5 x 7.S x .6 cm thick were then placed across
the cows 2.5 cm apart. A sketch of the copper blocks in a measurement position
is sho_n in F18. 7. Care had to be taken so that about the same area of fiber
was contacted each time and the contact pressure of the reslstm_ce measurement
leads was the sane. A volt-oh_ m_cromameter uhich had a noncLnal input impedance
of 100 K ohms per volt DC was used to record the resistance. T_e resistances of
fibers coated using the orgm_o-silicone approach were also measured by this
ce chnique.
Another method of resistance measurezenc was developed to provide a contin-
uous mouicorfng of yarn resietm_ce for the CVD SiC coaf:tng process. This was
done by p_ssing the coated yarn over two electrically isolated copper rods after
it exited from the in-line oxidation furnace and before the yarn was collected
on the take-up drum. The copper rods were offset in the vertical plane to
assure a constant tension sliding contact. A photograph of the CVD SiC coatfng
apparatus rich the continuous resistance measuring copper electl_odes in place is
shown in Fig, 8.
2.2.2 Arcing Tests
An open circuit test was used to deternine £f the CVD coated graphite fibers
would arc when placed across open electrical leads. In this apparatus, t_o copper
electrodes were placed £n the bottom of a Teflon lined Lucite box and the output
of a 120 VAt Varlae with an in-line voltmeter was connected to these copper elec-
trodes. An experimental setup is shown L_ Fig. 9. The tube that can be seen
between the copper plaCes in the phrtograph is a piece o,t almEtnum oxide used to
prevent accidental contact between _ he bare copper electrodes. To observe the
benefit of a CVD coating, an oxidized coating or one that had been in-l__ne oxi-
dized, a 6 c_ length of the yarn to be evaluated was placed across the Oeo bare£1at copper electrodes. The spacing of the electrodes wa_ ma4ntalned at 1.3 ca.
The voltage was increased fro_ 0 Co voltage breakdc_n.
2.2.3 UltJdaate Tensile Strength }4essurements
2.2.3.1 Single Fllameut Tests
The tensfle strength and modulus of individual fibers were measured for the
uncoated, C__ _.oated, and oxidized CUD SiC coated yarn in a UTRC teat apparatus
(Ref. 5) wh£c ad been de,eloped for fine filament testing. This technique
involved the extraction of single f11a_nt from a tmlti-£iJmnent bundle for
attachment to the test apparatus. Careful calibration of the load cell and
croeshead movement allowed for the calculetlon of both ultimate tensile strength
from the breakiu8 load trod uodultm from the elastic portion of the stress-strain
curve. A pk,otosraph of the apparatus is shoeu in MS. 10.
A Kin_mun of ten fibers which broke /n the 8age length were used to deter-
a_ne the averase tensile strength of the fibers. The ares of an individual
fiber _ich yes used in the calculatlon of teus£1e stremgth was Inltlally oh-
rained from the averase of 50 plsnlmeter measurements. These measurenenUs were
made from 1000X photomicrographs of _ounted cross sections of the yarns beingtested.
2.2.3.2 Yarn Tests
There is no ASTM accepted standard for measuring tensile loads or strengths
of h£sh modulus graphite yarns. Tensile measurements of graphite fiber coated
using the organo-sllicone approach vere _ade using the whole yarn. The specimens
were prepared by £mpregnation of the graphite yarn wi_n a 45 w/o solution of epoxy
resin (Ppon 828/ScQtte 21, 100g/19g) in uethylethylketone. The resin £mpresnated
yarn bundle was pulled taut, fixed in this position and allowed to cure at room
temperature overnight. The cured res/a 18pregneted yarn wu cut into 13.9 ca
spectmmm (or 10.9 cm specimens) md placmd as an el*--4num plate. Each and was
reinforced with 4.2 on pieces of the same impregnated yarn by bonding it with
epoxy resin (described above), at the same time as 2.5 ca square cellulose tabs
were bonded to the andes using Epon 907 adhesive.
Yarn tensile specimens were measured on a 890N Instron using pneumatic air
driven grips t_ hold the specimens, at a crosshead speed of 0.05 ca/uln. A
specJJaen gage lensth of 2.5 cm or 5 cm was used.
2.2.4 Coating Thickness 14easurements
An initial goal of this program was to obt_dn coating thicknesses on indi-
vidual fibers of approximately 0.10_m. These coat£ngs were too thin to measure
accurately even at IO00X w£ch convenutonal metallosraphy. Frsparations of mountedcross sections were then examined in the gEM with both chemical etchant and ion
u411tng used Co obtain edge relief. Specimens were also prepared and ex_ined
with an electron uc£croscope.
2.2.5 X-ray lYlffractiou Analysls
The coated graphite fibers _re formed into t2iated yarn smtpl_ approximately
2.5 ca Long and mounted £n 8 standard Debye c_era having a radius of 117.5 an.
Copper k_ radiation was used at 40 kV and 20 me. settings. An 8 hr exposure was
typical for all samples in this series. During exposure, the yarn sample was
rotated to /_sure 811 possible planes within the spec_len were presented to the
X-ray beam. After the developaen. _ o£ the £LIm direct comparisons mere made of
each film with a standard SiC, Si3N _ or BN X-ray diffraction pattern. In the
ease of the fibers costed by the orgsno-slllcone process, no pattern except that
of rbe graphite fiber was ever observed, so it was assumed that the coating on
these fibers was morphous.
2.3 Composite Test Procedures
2.3.1 Epoxy Resin Flexural Strength Measurements
A resin formulation containing HY720, epoxy Novalsc DEN 438, and curing
agent 4,4'-diamlnodiphenyl sulfone (DDS) in the weight ratios, MY720/DEN 438/
DDS of 4.5/i.0/2.25 was developed for use as a resin matrix in sraphlte/epoxy
co_posltes. The epoxy resin system was designated UTRC-89Z. Flexural speci-
mens were prepared and measured according to ASTM procedu:e D790-71. The
specimen dimensions were I0 ca x 1.25 an x .47 c_a.
2.3.2 Fabrication of Graphlte/Epoxy Prepreg Tape
Forty-five weight percent solution of the UTRC resin in a 50:50 weight per-
cent of methylethylketone and celltmolve was prepared for tmprepa¢ion of
untreated graphite f_ber and $4C coated graphlCe fibers. The objective in the
Inlci&l coating process was to obted_ a resin coated 8raphlte yarn contalnin K
33-35 w/o resin, in order co obtain a fiber volume percent of approxhaately 60Z
in a finished composite. Using the above solution, a graphite tape containing
43 w/o resin was produced and a eo_oeite urlth a fiber volume of only about 48Z
w_s formed, In order to decrease the resin content to 33 w/o in the Krrph_te
prepreg_ the concentration of the iaprelnation solution was reduced to 35 w/_:,,
Resin ilpregnated tape 8.8 cm_rIde was prepared by passing the untreated
or coated yarn through the resin solution via pulleys and then winding onto a
45 cm diameter drum. The tape was allowed to stand at room temperature £n a
hood to remove solvent. It was then cut Into the appropriate size for fabrl-
cation into a composlce, and placed in an oven at 298 K for I hr to remove
excess solvent.
2.3.3 Fabrication of Graphite/Epoxy Composites
The solvent free precut capes are stacked one over the other to yield
layered composites 3.75 ca x 20 ca • .25 ca or 8.8 ca x 16.3 ca x .5 ca. The
uncured lay-up was sealed £n a nylon bag for vacuum moldJm4g. The bag was evac-
uated and the temperature was raised co 398 K, and maintained at chls temperature
for I hr. Pressure (690 Pa) was appl/ed after I hr at 398 K. The tA_tpersture
was raised to 423 Kp _d held at this temperature and pressure (690 Pa) fo_ 1 hr.
The composite was cured for an additional hour st 453 Ks while at 690 Pa,
2.3.4 7Lezur_ Property Mmure_ent
The spec_tuen8 used £n detendnin& flezural properties had a nouinal stze
8.8 ca loug x .63 ca vide x .25 ca thickness, and were leuured either by a
3-po£uc or /,-point method at a span-to-depth ratio of 32/1 or less, according
co ASTM procedure D790-71.
2.3.5 Shear Strength Measurement
The specimens used Ln determ/ntng the lnterlamtnar shear strength had a
no=trial size of 1.5 cm long x .63 cm wide x .25 cm _hlck, and vere measured at
a span-to-depth ratio of 4/I.
3.0 DISCUSSZO_ A_D _SULT3
3.1 C_D SiC Coning Approach
l_e CV_ deposition apparatus as modified for continuous monitoring of yarn
resistance was also used to demonstrate the feasibility of coating graphite
yarns. These yarn_ chosen for the CVD SiC process _ere HMS, Cellon 6000, and
T-300. Celion 12000 was also selected when during the course of this program
unsized Cellon 6000 yarn yes no lo_ger co_,erclally available. Although indi-
vidusl filament diameters within different graphite yarn bundles were all
about the same, the number of filaments per tow varied considerably. The
graphite yarn was composed of 10,000 filaments, T-300 graphite yarn contained
1400 f£1aments per toy and Cellon 6000 and Cellon 12000 contained 6000 and
12000 lilaments per tow respectively°
Since the final task of this program was to mupply NASA vlth epoxy resin
co_osites containing the highest electrical resistance and reasonable strength
CVD S£C coated _raphite yarn of each of the above types of graphite tows, experi-
|.mrs were conducted which were directed toward achiev£ng thim goal. A range of
drawing rates from ].5 m/tin to 122 em/a_n and the _-line oxidation furnace off
or at a temperature of 773 K or 873 K _ere chosen as the overall matrix of
operating paraReters to bracket those conditions thet would possibly yield the
highest CVI) SiC coated yarn reststa_ce. This matrix is shown in Fig. 11.
_n Tables 1, 2 and 3 are listed the experimental runs £or Celion 6000
graphite yarn, T-300 lraphlte yarn, end _ graphite yarn for chis drawing rate
and io-line ozldmtion furnace temperature Ntr£x. there are two sets of rests-
tance values for each run which is l_s_ed _n these tables. The first set was
taken i_medlately _fter the rum was made and the second set was made on the s_e
length of coated yarn at a different t._ae to darlene the repeatability of the
measurement. For most runs both these sets of resistance _easure_ents did not
di£fer greatly. Fron exa_ntng the overall resistance data in the three
tables, it appears that fibers prepared at the hi&her drayS,& rates (90 C_/_L_n
and 122 cm/min) are not affected by in-line oxidation temperature levels. This
is probably due to the extreme short resldenc_ t1_e of the CVD SiC coated
graphite yarn _dthin the oxidation furnace st these high rates. The electrical
resistance of the coated yarn does appear to increase _ith decreasing drab_ng
rate. However, the results at the slowest draying rate, 15 ca/sin are not
consistent. In general, these graphite yarns seem to run best through the
reactor at speeds greater than 1_ cm/mln. This is particularly true for yarns
in-line oxidized at the higher temperature of 873 K. The Celion 6000 graphite
yarn and the T-300 graphite yarn under these conditions of Io_ dravtng rates
and high In-l_ne oxidation temperature continually clogged inlet and outlet
reactor parts so severely that no coated yarn could be collected st these con-
d£tions. In the Lid-speed drawing range the coated HMS and Celion yarns had
higher resistances than the T-300 coated yarn.
I0
_.- :: • ....
Individual fiber tensile tests were made on the C_D SiC coated ENS a_d CVD
SiC coated CeZlon 6000 graphite yarn from these rums. The results of these tests
are 1/seed in Table 4 for the Celion graphite yarn and Table 5 for the HMS
graphite yarn. The pretb_st of the as-received T-300 graphite yarn made it too
difficult to extract individual fibers long enough for tensile testing. For the
CVD SiC coated Celion graphite yarn at a_ in-llne oxidation temperature of 773 K the
ultlmace tensile strength appears to peak (2333 HPa) at 30 ca/aln and then teper
off (1736 _Pa) as the drawing rates i_cr_ase to 122 cm/n_n. Examining slmilar
data (Table 5) for the CVD SiC coated B]4S yarn the In-llne ox/dation teeq_erature
of 873 K yields the more consistent (2200 M_a) ultimate tensile strength.
Comparing electrical resistance, reasonable tensile strength, and taking
into account qualitative information such as smoothness of reactor operation,
amount of yarn fraying during processing and handleabiliry during evaluation,
the following operating parameters were chosen for each graphit_e yarn. For the
C_ SiC coated Celion 6000 graphite yarn an in-line oxidation temperature of
773 K at 30 cm/min resulted "in a combination of an ultimate tensile strength
average of 2333 M_a (339) and an electrical resistance average of 1.5 K ohms.
The parameters chosen for the HMS graphite yarn were drawing rates of 30 czJmin
and an in-line oxidation temperature of 873 K. These conditions yielded CV_ SiC
coated _qS graphite yarn which had an average individual fiber tensile strength
of 2145 MPa (311 ksi) and a relatively high electrical resistance of 2.7 K ohms.
For the T-300 graphite yarn deposition conditions of 30 ca/_n with an in-line
oxidation temperature of 773 K was chosen. For these conditions the CVD SiC
coated T-300 graphite yarn had electrical resistances as measured with the
copper block technique of 750 ohns.
Toward the completion of this program and before all the coated graphlte
yarn had been produced for complete composite evaluation the future ava_labillty
of Calion 6_00 graphite yarn became questionable. The same Ranufacturer was
o_ly able to supply unslzed graphite yarn in a 12000 filament tow form, Cellon
12000. CVD SiC coating experiments were made with this yarn at only one drawing
rate, 30 cm/min, l'ne in-llne oxidation furnace was used at 773 K and 873 K.
The resistance data for chase runs are l_ted in Table 6. Individual filament
tests were made on extracted fibers fro_ this series of runs and these results
together _rlth tests on fibers extracted from the u_treated graphite yarn are
l_ted in Table 7. From the data in these t_o t_bles, the in-line ox/dation
temperature of 773 K was chosen as )fielding the best co-;bination of strength,
2355 l_a (3_2 ksi) and average resistance, 1.A K ohms. These deposition con-
dltio_s were used to produce enough Cellon 12000 coated yarn for co_poslte
fabrication.
11
The paraueters for the four types of graphite yarn along with reactor gas
input and temperature of deposition are 11sted in Table 8. These chosen condi-
tions were used to produce enough coated yarn of each type for incorporation
into deliverable composites for NASA.
3.2 CVD Si3N 4 Coat/n 8 Approach
The chamlcal vapor deposition of silicon nitride ,_to HTS, _ and Cellon
6000 graphite yarn was investigated. The deposition of CVD Si3N _ involves the
following gaseous chemical reaction:
3SiF_ + 414T13 + Sl_. -4. 12 _F
At UrRC it was found that this reaction when conducted at telperatures of
approxi_ately 1723 K and pressures of approximately 1 tort produces a dense, im-
pervious, high resistance silicon nltrlde coating on bulk graphite substrates.
In the large cylindrical deposition apparatus previously shown in Fig. 3, HTS
graphite yarn was suspended in the center of the hot zone and CVD Si_ experi-
ments were run for 5, 10, 15, 30, 45 and 60 rain durations. Since only a 20 cm
length of yarn was coated at one t_me, nultiple exper/_ents had _o be made to
obta4n sufficient coated material for evalustioD. In Figs. 12 end 13 are shovn
cross sections at 1250X for CVD Sl_ coated HTS graphite yarn selected from
runs of duration 5, 30, 45 _d 60 _tn. Froa these figures it c_ be seen that
the thickness increases with time and after extended periods (Fig. 13) the
coatings become so thick that the reactant gas cam no longer penetrate the yarn
bundle. It was encouraging to observe that even in Fig. 13, ind/vidual fibers
are s_ill completely coated before fiber bridging occurs.
Successive X-ray diffraction patterns of the siJicon nitride coated HTS
graphite yarn were taken and are shown in Fig. 14. As would be expected, the
strongest X-ray patterns were obtained from those H_S yarns which were r_ for
the longer duration hence heavier silicon nitride coatinp. A standard o Si_
pattern is also sho_u in this figure for comparison.
Another apparatus (that was shown in Fig. 5) which vas much s_aller in
volume was developed for 8raphlte yarn deposition. This new apparatus decreased
pump down time, t1_e to cool after deposition, etc. Initial runs wlth HTS yarn
_ere made to assure the same quality of coatln8 _ould be obtained in this
apparatus as was previously achieved in the large CVD coating apparatus. In
table 9 are shown some individual fiber ultlaate tensile strength and uodulus
data from extracted f_rs from CVD Si3N _ HTS coated graphite yarn coated in
the large and in the s_aller _pparatus. Included in this table are results from
two HTS yarn_ which were exposed to /.5 s4n deposit_ton cycles in each apparatus
except that no reaetmt gas e_s introduced for these yarns. These initial ulti-
mate t,n_ile strength data £ndicate that the Zarge depoalt_on furnace environment
appears to cause slightly more degradation to the an-received yarn properties
than does r_e smaller deposit_on apparatus,
12
SgNstudies of these runs listed in this table were then conducted to observe
the surface of the silicon nitride coaLl_gs. In Figs. 15, 16 and 17 are shown
CVD St3N _ coated HTS graphite fibers from deposition rims at 1673 K for 5, 1D
and 15 rain durations. In Figs. 18, 19 and 20 are shown fibers made at 1593 K
deposition temperature again for t/Jes of 5, 10 and 15 rain durations. For corn-
par/son purposes, a SEM photograph of the surface of as-received HTS yarn is
shown in Fig. 21. In Figs. 15 Chrou8 h 17 the coating can be seen to be develop-
ins in thickness for l_ser deposition times. The surface differences In Figs.
18 through 20 are probably due to the lower deposition temperature. In Figs.
18 and 19 can be seeu the start of bridging of the coating between two fibers.
The surface debris shown in Fig. 20 could be due to the lonEer deposition Clmes
at this lower than normal deposition temperatcre.
To determine if excess SiF_ in the reaction chamber was causing a loss in
tensile strength of the CVD Si3N _ coated HTS yarn experiments were made with
the SiF_ gas flow input consist _ald varying amounts of mmonia introduced. For
this series of runs the deposition times were of 10 and 20 rain titration and
deposition temperatures of 1593 K and 1673 K. In Table 10 are listed the re-
sults of individual fiber tensile tests on these coated yarns. The reason for
the slightly lower tensile test results from these deposition condit_lons than
those reported Ln the previous table is not known.
pzslstance measurements (except Co establish resistances of greater than
106 ohms) via the copper block technique developed for the CVD SiC coated
graphite yarns could not be used for the CVD $43N _ coated graphite yarns since
the resistances of the Si3N _ coated yarns are too high to be in the range of
the volt-microamneter used for that technique,
The qualitative arcing apparatus was used on lengths of coated yarn from
each of these rums. 1he results of the arcing tests are given in Table 11. In
EtherS1 no experimental _ of 20 rain duraLton sho_ed evidence of arcin 8 rich
an open circuit voltage of 120 YAC. Thus the behavior of each pair of runs does
indicate chat the longer CVD Si3N_ coating runs do protect the graphite yarn
better than the shorter runs. Data for an uncreated HTS yarn are included in
this table for comparlso_ of Its arcln S behavior.
Static CVD Si3l|_ experluents were made w£th HMS graphite yarn at four a_monla
to silicon tetrafluoride ratios of 1.93, 3.72, 6.01, and 8.45 for deposition
temperatures of 1523 K, 1623 K, and 1723 K. All of these runs were of 20 mln
duration. In Table 12 are l_sted the gas flows, l_13/SiF_ ratios_ and the results
of ult_La_e Denslle tests on Indlvldual fibers extracted from the coated HMS tows.
From exaz_Lning the ult/mate tensile test results in this table, there were three
conditions which showed no decrease in tensile strength and three more In which
the decrease in strength was less than 151 of the _-recelved tensile strength.
The first _hree deposition conditions were at temperatures of 1623 and 1523 K
but the second set included a deposltlon condition of 1723 ._ (Run SN-44),
13
In an attempt to develop a correlation o£ thickness with time and gas input
flow ratio combinations of experimental runs were made at flow ratios of 3.72,
6.01, and 8.45 for 5, 10 and 30 rain durations. All these runs were made at a
deposition temperature of 1723 K. In Table 13 are listed the operating param-
eters for chess runs. _hotomicrographs of the cross section of CVD $i3._ coated
H._ yarn for all three ratios for the 5 min duration experiments are shown in
Fig. 22. The IO rain deposition experiment_ are shown in Fig. 23 for the 30 mln
depositi0_ experiments in Fi_. 2_. The thlcknes_ of the silicon nitrlde costing
can be seen to be increasing with increasing times of deposition. The ion&
deposition time tends to start producing clusters of coated fibers (Fig. 24).
The elongated appearance of the graphite fibers in some of these photomicro-
graphs Is due to off-axls specimen mounting during metallographlc preparation.
So clear correlatlon with coating thickness and h143/SIF _ ratio could be ex-
tracted from these photographs, individual fiber ultimate tensile tests were
attempted on these runs but no filaments could be extracted from the longer
duration runs (SN 78, SN 72, SN 80) and only short pieces could be tediously
extracted from the re_alnlng runs listed in Table 13.
To obtain coated IMS yarns which could be more readily tested, the same gas
flo_ ratios and deposition temperature were used but the times of deposltlo_
were 1, 3 and 5 mln. Individual filaments from these runs (except for run SN
95) could be extracted from the CVD SI3N _ coated H_S yarn bundle for testlns.
The results of the tests made on this series of runs are listed in Table l&.
From this table It can be seen that runs SN 93 ylelded values as hl_' _ 2458
MPa (357 ks£) and run SN 100 was also in excess of 2400 NPa (350 ksl).
These C_ Si3N _ coating experiments were conducted with one suspended tow
in the chemical vapor deposition apparatus for each run. To make a composite
of CVD St3,_L coated R_S yarn the yield of each deposition experiment was in-
creased by suspending 15 tows at one ti_e in the center of the hot zone. ,_Iodi-
flcatlons had to be _ade to the inlet gas flow path to accommodate thls increase
of suspended toys to prevent blockage o£ the gas £]_w path by _hese lar_er
number of tows in the reaction chamber. The reactm_t _as vas introc_uced at the
bottom center of the vertical cylindrical chamber, and as such the end of the
to_s nearest the gas inlet had the thicker silicon nttride coatin_. The top
Xeft photograph in FIg. 25 _as taken from the bottom end of the suspended toe
and the Si3N _ coating is fairly thick. The upper right and bottom vao czoss
section photographs In thls figure were taken from vertical locations of the
C_D SI3E _ coated H_ _raphite yarn which was used to fabricate a composite panel.
It can be seen from these cross sections that _he CVD Si3_ _ coat,us thickness
of lengths that went Into composites from these runs was less than 0.5 microns.
Static experiments _ith Celton 6000 graphite yarn were made at 1723 K d_po-
sition temperature and various times and reactant @as ratios. In Table 15 are
listed the parmneters for these runs which were made for _, 10 and 30 rain dura-
tions. Photomicrographs of cross sections of the CVD Si3_c ' coated Celion graphite
yarn made in the rtms listed in this table are sho_n for the 5 miu duration in
Fig. 26 for the 10 mtn exper/_ent in Fi|. 27. end for the 30 utn ezperinent in
Fig. 28. The behavior of the Celion 6000 graphite yarn in the depoei_on chamber
was similar to that of the HKS graphite yarn except at the longer deposi_Lon
times the corresponding thickness of CVD Si3N _ coating appears greater with the
Celion 6000 graphite yarn. As was prevlously shown with the CVD Si 3_._ coated
H_ graphite yarn (Fig. 25), at the longer deposition times brtdsir.g of the
coating across Celton 6000 f/bers also occurs (Fig. 28).
These fairly thick Si3N _ coatings on the Celion 6000 graph£te yarn pre-sented dlfflculty again similar Co the HHS coated yarn in that slngle filaments
could not be easily extracted, For this reason the C_D Sl3S _ experiments withCelion 6000 were repeated for the shorter (i, 3 and 5 zzln) run times. The
deposition par_ters and ult_ate tennile test results for thls series of
exper_nents are listed in Table 16. Even wlth these shorter deposltlon times,
slngle fllsments from runs SN 1.15 and SN ].21 could not be extracted for testlng.
Both Chest runs were of 5 rain duration, Although the _enstle strengths with
CVD Si3N_ coated Celton graphite yarn are not as .high ea those obtained with the
CVD S£3N_ HNS graphite yarn (see Table l&), values of 1860 to 2020 NPa (270
290 ksi) for runs SN 116 through SN 118 ere considered acceptable. These three
runs were all --,de at a_on/a to silicon cetrafluor£de ratios of 6.01,
The Celion 12000 graphite yarn vhlch was discussed earlier in this report
as having been received tmaard the end of this program was not completely eval-
uaZed for CVD Si3_ _ coatln K. In Tig. 29 is shown a cross section of CVD Si3N _
coated Celion 12000 graphite yarn that yes run for 20 udn at NH3/StF _ ratio of
6.01 and a deposition temperature of 1723 K. From _his and ocher preltninary
experiments it is felt that, other than any problems associated with handling
12000 fLlament _ as opposed to the 6000 filament ends in previously available
Cel£on 6000 graphite yarn, this new yarn should present no d£fficultles in the
CVD Si3N _ coating process.
3,3 CVD BN Coating Approach
The chm_cal vapor deposition of boron nlcr_de onto H_S and Cellon 6000
graphite yarn _as _nvesctgated. The reactant gases used for thi_ deposition
proces_ were boron trifluoride and _monia, The reactto_ equation can be ex-
pressed as:
BF 3 ÷ 1_I_ -_ B_ + 3_F
Previous work at UTRC had -..h_.a _hac bulk pyrolytic BN could be formed on
graphite substrate ac _e_era. "_-- _- _873 K under reduced pressures. Theseease conditlo_s therefore vex, _d in -.he first exper£sents vith HI4S _raphlte
yarn. Two 20 cm length8 of the ]_L _ov were suspended in the center of the
large vapor deposition apparatus that was shown in Fig. 3. Temperature of
15
deposition was held cons tat at 1873 K while experimnts were run for various
times of from 5 san to 180 rain. Another aeries of experiments were made in
which the time of depositio_ was held constant at 30 Etn and temperature of
deposition lover in 25 K increments from 1873 K down to 1748 K. These runs
are listed in Table 17. A plate of graphite _s also placed in the deposition
chamber fo; these last series of runs. This plate was used to measure the rate
of weiEht gain per unit area and rate of thickness growth. From the weight gain
measurements, it was felt that the deposition temperature of 1748 K was too low
to initiate formation of measurable amounts of BN. Electrical resistance mea-
surements with the copper block technique indicated that at least I0 nln of
deposition time at. 1873 K was needed to obtain an open circuit reading (>106 ohm)
on the CVD BN coated H}_ graphite yarn. For the 30 nin experlmeuts all except
the 1738 K run had tow resistances too high to measure.
3.3.1 CUD BN CeLion 6000 Graphite Yarn
Cellon 6000 graphite yarn was used as the substrate in the C_I) Bl_ apparatus.
The temperature of deposition was held constant at 1873 K and runs of from 1 to
45 mln were made. The CVD BN coating runs for Cellon 6000 graphite yam are
listed in Table 18o The shorter duration rams listed in this Cable (l to 5 mln)
were made to produce coated tows from which individual f_bers for tensile testing
could be extracted. Sections of coated yarn were taken from the runs listed in
this table for studying growth rate. In Fig. 30 are shown runs of 1 end 10 ,,in
duration. In Fig. 31 are shown cross sections of the 20 and 45 rain experiments.
The effect of longer deposition tim can be seen by eomparin K the CVD BN thick-
ness as shown in these two figures. The CVD Bg coated yarn from the 45 Idn
duration experiment was brittle and contained many areas of individual fibers
clumped together.
The extraction of single coated fibers for tensile testing on deposition
runs of longer than 10 rain was not possible. The 1 rain duration runs were not
a problem but difficulty was encountered with the 10 rain deposition experiments.
,'he results of ultimate tensile strength and modulus tests on the extracted CVD
BN coated Cellon graphite yarn are given in T_ble 19. The lower measured ten-
sile strength of 1180 _a for BN 19 compared with 2200 MPa of the untreated
CeLton 6000 graphite yarn was probably due to the exposure of the Eraphlte yarn
to r_e deposition teaperature of 1873 K at low pressures rather than the presence
of the CVD BN coattng. This effect of temperature c_m be seen with the results
of BN 16 which indicated a tensile strength of only 830 MPa after having been
exposed Co 10 m/n at 1873 Z compared with the 1 mln exposure of B.4 19.
16
3.6 _valuation of CVD S£C Coated Graphite Yams in Compoeites
Large cosposlte panels of untreated end CVD coated graphite yarn were re-
quired to be made and shipped to NASA at the completlon of th_s program. The
graphlte yarn for these panels was: HHS graphite yarn, Cellon 6000 graphite yarn,
T-300 graphite yarn, nnd Celion 12000 graphite yarn. Th_ CVD processing condi-
tions for each graphite yarn were chosen to produce the highest electrical re-
sistance with the least decrease in mechanical properties of the untreated
graphite yarn and were shown in Table 8. The epoxy resin required for these
panels was to be in all caBes the MY720 containing UTRC 89-Z resin. To evalu-
ate the U_C method of in-house £npregnatiou of yarn, tape _abrication, lay-up.
and laminate cure cycles, that were to be used to fabricate these deliverable
composites, s_a11 composites were made. These small composites were unidirec-
tional 6 to 12 layers thick, 3.8 cm wide by 7.62 cm long. Specimens vere cut
frou these panels for three point uodulus of rupture end short beau (s/d A:l)
r_sti_. Along _rlth the _fRC 89-Z resin, PR-286 and PR-288 epoxy resins were
used as natrtces for the L_ graphite yarn series. For the :ematning graphite
yarns only P_-288 m_d the L'rRC 89-Z resins were used for these small composites.
3.4.1 Statuary of Previous Studies eith CVD SiC Coated Graphite Yarn
Composites
At the conclusion of the previous progrm, couposite panels were made con-
sistin8 of three tTpes of HTS graphite yarn. These three types were: untreated
HTS graphite yarn, CVD SIC coated RTS rraphlte yarn, amd CVD SiC In-line oxi-
dized coated HTS graphite yarn. Each panel was composed of 16 layers of uni-
direetionml yarn 7.6b cn x 7.64 cm with a minimum 60Z volume fiber con_ent. The
resin used in these panels has been K/yen the notation UTRC 89-Z. This resin
wae co_posed of NY720, DE_ 438 and DD$ end was previously described on page 8
of this report. Flexural properties o£ the resin are listed in Table 20. The
composite specimens were numbered 212-6, 212-7, an_ 212-8. The first vas the
laminate made _Lth untreated HTS graphite yarn, the second contained CVD $_C
coated HTS graphite yarn, and the third con'_alned CVD SiC coated HTS graphite
yarn which had been glven an In-llne oxidation treatment of 773 K. Test specl-
mens were _achlned frmn these panels with s/d of &:l for sho_t beam shear tests.
The results of these tests are listed in Table 21 and the averages show
that the untreated HTS graphite yarn panel had a shear strength of 39.6 _a
(5.75 ksl). The CVD SiC coated HTS graphite yarn panel had s shear strength of
76 _Pa (II.0 ksl) and the CVD SiC coated HTS Kraphlte yarn that had been Kiven
an £n-llue oxidation treatment at 773 K had a shear strensth of i01 14Pa (l&.6
ks£). The latter shear stren_h values Indlcate that the ox_datlon step treat-
ment of the CVD SiC coated HTS graphite yarn promotes bonding in the UTRC 89-Z
reslD.
17
3.4.2 CVD SiC Coated ILNS Graphite Yarn/Epoxy Colpos£tes
The untreated IL_ graphite yarn was initially used with both the PR-286 and
PR-288 resin systems to make the small evaluation composites. Test results from
these composites are listed in Table 22. The average flexural strength, modulus
of elasticity and shear strength for each composite can be compared with the last
entry in this table which was taken from Hercules data sheets. This comparison
would indicate that the in-house impregnation of yarn, tape fabrication and lay-
up, and conposite cure cycle can produce acceptable finished composites. The un-
treated !L_S graphite yarn was then used to prepare small composites with the
UiRC 89-Z resin. The results for the mechanical tests of specimens cut from
two of these panels are listed in Table 23. The overall average of 756 MPa (110
ks£) for the fZexural strength and 42.5 H_a (6.2 ksi) for short beam shear are
both lo_:er than similar values obtained in the PR-286 and PR-288 resins.
The CVI) parameters were chosen Co produce the highest electrical resistance
coated and oxidized B.v_ graphite yam. This CVD SiC coated HHS graphite yarn was
then used to make small composites in UTRC 89-Z resin. The results for the mechan-
Ical tests of specimens cut from two o£ these panels are listed in Table 2£. From
this table it can be seen that for the UTRC 89-Z resin the CVD SiC coated HMS
graphite yarn produces an improvement of from 42.3 NPa (6.1 ksl) up to 62.8 MPa
(9.1 ksi) in shear strength. The flexural strength of the coated yarn also shoes
a slight improvement of from 756 HPa (ll0 ksi) for the untreated yarn to 867 MPa
(126 ksi) for the CVD SiC coated IIMS graphite yarn.
3.4.3 CVD SiC Coated Cellon Graphite Yarn/Epoxy Composites
Untreated Cellon 6000 graphite yarn was used to make six small composites.
Three o£ these employed PR-288 and the other three used UTRC 89-Z as the resin
matrix. The mechanical test results of specimens cut from these six panels are
Listed in Table 25. In the PR-288 system, the untreated Celio_ 6000 graphite
yarn yielded the highest combination of properties obtained with carbon-sporT
composites in this program. The averages of composites T62A, T62B, and T69
yielded 1854) HPa (268 ksi) for the flexural ._treng_h and 95.1 MPa (13.8 ksi) for the
short beam shear strength. With the UTRC 89-Z resin the averqe glexursl strength
of 1638 }IPa (238 ksi) was more than satisfactory but the average shear strengths
were only 44.6 _Pa (6.5 ksl) with this resin system for the untreated Calion 6000
graphite yam.
CVD SiC coated Celion yarn that had been oxidized at the temperature that
yielded the combination of the highest electrical resistance with the least de-
crease in individual fiber strengths was used to make five small composites.
These five employed UTRC 89-Z as the resin matrix. The resulr_ of mechanical
tests for this group are listed in Table 26. For the CVD SiC coated and oxidized
18
Celion 6000 graphite yarn in the UTRC 89-Z resin the averages of the five coi-
posites listed in Table 26 yield 833 I_Pa (121 kat) for the flexural strength
and 62.1 MPa (9.0 kst) for the short bean shear strength. The average flexural
strength for the coated yarn was less than that obtained _rlth the untreated
yarn 833 _Pa (121 ksi) compared to 1638 }/Pa (238 kst) in the UTRC 89-Z resin.
The shear strength on the other hand yam slightly higher, 61.2 MPa (9.0 ksi)
compared to 44.6 D_a (6.5 ksi) for the untreated yarn.
3.4.4 CUD SiC Coated T-300 Graphite Yarn/Epoxy Composites
The T-300 graphite yarn because of its relatively small number of filaments
per tow and twist present in the as-received yarn was the most difficult graphics
yarn to handle in both the CVD process and in tape making procedures used for
composite fabrication. Only five of the small composites for evaluation were
made _-lth _-300 graphite yarn. The mechanical test results of these five com-
posites are listed In Fable 27. The first three composites (T73, T77, T78) were
made with untreated T-300 graphite yarn In the UTRC 89-Z resin. The last two
composites listed in this table were Y84 and T85 vhlch were made with the CVD
SiC coated and ox£dlzed T-300 graphite yarn. In the UTRC Bg-Z resin the un-
treated T-300 graphite yarn yielded averages of 1489 l_a (216 ksi) for the
flexural strength and 56.6 MPa (8.2 ksl) for short beam shear strengths. Com-posites T78 in this series had values of 1654 PIPe (240 ksi) for the flexural
strength and 84 _IPa (12.2 ksi) for the shear strength. This particular compos-
ite compares favorably vlth the optlmum desired properties for this systemcombination.
The CVD SiC coated and oxidized T-3_O graphite yarn was used to sake only
two small composites and ¢hese were both with LrrgC 89-Z resin. The averages
for these two composites were 673 _Pa (97.6 ksi) for the flexural strength and
78.6HPa (ll.4ksi) for the short beam shear strength. The flexural strength
values are lower for the CVD SiC coated T-300 graphite yarn compared ¢o the un-
treated T-300 graphite yarn In the same U_C 89-Z resin but the average shear
strengths for the coated yarn are higher 78.6MPa (11.4 ksl) compared wlth 56.6
HPa (8.2 ksl) for the untreated T-300 graphite yarn. These lower flexural
strength values are felt to be due In part to the dlfflculty encountered In
making these composites. Thls dlfflculty was attributed to the previously
discussed poor handleablllty of the CUD SiC coated T-300 graphite yarn.
3.4.5 CVD SiC Coated Celton 12000 Graphite Yarn./Ep0_- r .... ,.^_
The Celton 12000 graphite yarn as was discussed previously had become avail-
able late in this program. Because of this lateness only four small composites
were made for evaluation. One of each of the following: untreated Celton 12000
graphite yarn in PR-288 resin (Tgl); untreated Celton 12000 graphite yarn in UTRC
89-Z resin (T95); CVD SiC costed and oxidized Cellos 12000 graphite yarn £n PR-288
resin (T93); and CVD SiC coated and oxidized Celton 12000 graphite yarn in L"fRC
19
89-Z resin (T94). The test results o£ specimens cut from these four composites
are listed in Table 28. The shear strengths for the PR-288 resin system of 110
MPa (16.0 kel) and for the UTRC 89-Z resin system o£ 103 NPa (14.9 ksl) for both
these untreated Ce/ion 12000 graphite yarn composltes are considered more than
acceptable.
The CI_ SiC coated Cellos 12000 graphite yarn In the PR-288 resin averages
of 1288 MPa (187 ksi) for the flexural strength and 105 MPa (15.3 ksl) for the
short beam shear strength compare favorably with those obtained with the C_ SIC
coated Cellos 6000 graphite yarn previously described. In th_ L_RC 89-Z resin,
the CVD SiC coated Cellos 12000 graphite yarn composite ylelded averages of I142
_Pa (165 ksi) for the flexural strength and 73.1 HPa (10.6 ksi) for the short
beam shear strength. These results are slightly better than vhst had been
achieved with the CVD SiC coated Cellos 6000 graphite yarn in this resin system.
3.4.6 Sumnary of C_ SiC Coated Graphite Yarn/Epoxy Composite Data
The test results iron the small composites made for evaluation vlth UTRC
89-2 that hays Just been described are su_axi_d in Table 29 for the various
comblnatlons of untreated _nd treated graphite yarns. From this table it can
be seen that in general r_e flexural strength is lower for Cellos 6000 and T-300
graphite yarns £n the UI_C 89-Z resin system. The CVD SiC coated yarns in m0st
cases when incorporated in the UrRC 89-Z resin yield shear strength results close
to 68.9 Ira (IO ksi) whlch was correspondin&ly higher than those for composites
containing the untreated yarns in this same resin.
3.4.7 Composites Delivered to NASA
Large composites 7.6 cmx 7.6 ca by 16 unidirectional plies were required
by NASA from this prograRfor burn tests. In Table 30 ere listed these deliver-
able coqposiCe panels with a description of the graphite yarn and CVDSiC/O 2
treatment when used. All of these composite panels were made with the U_RC 89-Zresin as a matrix.
3.5 CVD Si31_ 4 Coated ItNS Graphite Yarn/Epoxy Composites
CVD S£3N_ coated ti]4S graphite yarn f;oa the multiple yarn deposition ex-
periments were put into a compo_ite panel with PR-288 epoxy resLu. These compos-
ites _ere made by coating _dlvldual CVD Si_N_ coated HHS graphite yarn tows vith
resin and hand plat/rig them in the small composite panel die. The results of
_echan_cal tests of specimens cut from these small composites are listed in Tab!e
31. The emnual control of spacing i_proved _s each composite wm prepared (T88
through TgO)o Com_oslte TgO was by far the most cosmetically ecceptmble panel
mid yet the modulus of rupture results of al_ three p_els listed In Table 31
are fairly close.
2O
The averase of the _oung'8 uodulus of all three panels when conpared to pre-
vious ruults with _ graphite yarn indicate that the we',use fraction of in-
corporated sraphlte yarn was sliehtly more th_n half of what had been previously
achieved using continuous yarn-tape fsbrlcatlou processes. These ccaposites, due
to the hand lay-up process, were resi_ rich. The average modulus of elasticity
of_ these panels as listed in this table was 103 CPa whereas a 60Z volume fraction
ID_ 8raphlte yarn panel is typically 182 _'Pa (see Table 22). Hornalising the
obtained £1exural strength by the reels o£ modulus of elasrAcit7 of 60Z valise
fraction to that obt=tned would yield flexural strengths of 8pprozt_tely 1096
HPa (159 ks£). These values are definitely in the .-arise of H_-spox7 couposito
results, and if this nornLl.:l.sat:l.on is JusCif:Lad would indicate thac the CYD Si3N,,
coating process did not eign/ficantly desrade _.he _S graphlte yarn.
3.6 Discussion of Orgauo-SillconeApproach to Develop Coated Graphite Yibers
with High Electrical Reslstance
3.6.1 Results of Previous Studies - Static Test Runs
In the orKano-silicone coating experiments, the obj]ective yes to determine if
the graphite filaments could be coated _rlth an orsano-silicone precursor, and
throuKh pyrolysis convert the organs-silicone to a continuous coating of
amorphous silica.
In the first year's effort, four types of silicone materials vere selected
for these experiments by the static method. Two of these were monomeric silanes,
capable of foz_tng a polyneric Kel on the fiber surface, and _o others were
solub2e silicone pzepolymers. /mother cz/teria og selection was chat each ma-
terial vou/d be capable of undergoing decomposition _o mostly silicon d_oxide,
conta/nlng little or no silicon carbide.
The _ilanes selected were_ethyltriethoxysilane (HTS) and vinyltriacetoxy-
silane (VTS). The prepolymerB selected were CE silicone resin SR-355 and a
commercial prepolymer of ethyl silicate (ES). The materials selected are listedin Table 33.
The procedure used to coat HT$ graphite yarn by the static method and de-
tails of _hese static experiments were described in Ref. 4. As a result of the
statlc tests, which are summarized in Table 33, one materlal, a co, mercia1 pre-
polymer of ethyl silicate (ES), yes selected for studies _n a continuous
coating apparatus.
2_
3.6.2 ResuLts of Previous Coating Experlments in a Continuous Reactor
As _mtioned above in the first year's effort, ethyl silicate prepolymer was
selected for additional studies to cost HTS fiber on a continuous basis. Silica-
like coated HTS fibers produced in this continuous reactor were evaluated for
electrical resistm_ce, oxidation resistm_ce at 703 K for 8 hrs in static air,
tensile strength, 8nd for coherency of coating by SEH observations. Silica-like
coated HTS fiber _ith optimam properties was selected for further evaluation in
a unidirectional composite. The data _,ere presented in the first year's
report.
From the shear data in that report, it was concluded that the sillca-like
coating had caused a decrease in the adhesion of the epoxy resin to the coated
fiber surface. This suggested: (1) that the coating layer was poorly wetted
by the epoxy cesln or (2) that the coating ccnsisted of a mechanically weak
boundary layer. The physical appearance of the fiber suggested that the
coating produced a mechanically weak boundary layer. Experiments designed
to improve the silica-like coating to increase the electrical resistance of
the fiber and the shear and flexural properties in couposites were carried
out during the second year's effort. In addition to additional studies with
ethyl silicate as a coating material, three other materials were evaluated
in this program. These are C_ens-Illinots glass resins 100 and 650, and tri-
n-butylborate.
3.6.3 Studies Using F_iified Continuous Coating P_actor
I_e continuous reactor used in the first year's effort was modified to
carry out the coating studies during this period. The modified continuous coating
reactor is shown in Fig. 6. Celion6000 graphite yaru was used instead of HTS
graphite yarn as was done in the previous work. As mentioned above, four materials
were selected for evaluation as coacingn_terials. They were ethyl silicate (ES),
Owens-Illlnols glmss resins 100 and 650, and trl-n-butylborate. The results of
these studies for each coating material are described below.
3.6.3.1 Ethyl 511icate Costing Studles
A series of coating studies was initiated with Celion 6000 sraphite _arn
instead of _TS graphite yarn as was done in the previous work. Ethyl silicate
solution was used as the coating medium. The conditions of the coating runs and
the effect on the fiber properties are listed in Table 3&. The highest resis-
tance generated from this series of runs in which the ethy! silicate concentra-
tion was varied from 2.5 to 10 w/o is 180 ohm. The conditions for this run
(5 w/o, steam 393 K, drying rate 0.91 m/udn, pyrolysis temperature 1093-1173 K)
were repeated several times. In each case, this resulted in a lo_er resistance
22
(27-95 ohms) than experienced in run #50-16. The p_der-like appearance of the
coatins on the surface suuested that the coating £s easily removed causin$ this
variation in resistanceo
As indicated in Table 34, initial pyrolysis studies wteh the ethyl silicate
system were carried out at 1093-1173 K in nitrogen. Therefore, a aeries of runs
using ethyl silicate at two levels of resin concentration, 2.5 and 3.5 wt Z, for
application to Celion 6000 graphics yarn was carried out at a lower pyrolysis
temperature to dete_lne its effect on electrical resistance. The results of
these tests are also listed in Table 34. It is clear from the run made at 473 K
in steam that this low temperature treatment generated a coating with high elec-
trical resistance, relative to the high eemperature treatment (1093-1173 K). It
is also apparent chat steam treatment improves the resistance of the coating.
The 573 K treatment also improved the electrical resistance of the ethyl silicate
coating, relative to the IO93-1173 E treatment, buc not nearly to the same ex-
tent as the 473 K treatment. Based on these results, ethyl silicate, appeared
to be an attractive candidate, as a coating material for increasing the elec-
trical resistance of the graphite fiber surfaces.
3.6.3.1.1 Fiber Properties
The effects of the coating process on the tensile strength of coated fibers
which ah_ed good electrical res4=tance were dete_ned. In addition, the weight
percent coatin 8 on these coated fibers, end by calculation, the approximate _hick-
ness r_is coating would represent was also deternined.
The weight percent coating and tensile loads for the ethyl silicate coated
fibers are listed in Table 34. It should be pointed out that a 20 w/o increle
in fiber weight is equivalent to about 15 v/o increase in the fiber volume, when
the dens_cies of the Sraphtte fiber and silicon oxide coating are taken into con-sideration. If the dim_eter of the fiber increases from 8 x 10-" cm to 9 x 10 -_
cm, this would amount to a 26.5_ increase in fiber diameter. This suggests
that Increases in £_ber weight £rom 20 to 35.3 w/o correspond to costing thick-
nesses of 0.75 to 1.0_ This is she range o _. fiber welghc _ncrease_ generated
in coating of C_lion 6000 graphite yarn with ethyl silicate at the concentration
level_ and drying rate (0.91 a/m4n) used in these studies. Relative to "as-
received" Celion 6000 graphite yarn, high electrical resistance yarns from runs
SG-48, -49 and -50 e_hib4t the same tensile properties, indicating chat the
coating or coating process does not degrade the fiber. Silica-like coated yarn
from the hiEh temperature runs 5C-19 and -20 appeared to have undergone degra-
dation (560 co 467.N vs 636N for "as-received" yarn).
23
3.6.3.2 Glass Resin 100 Coating Studies
I_o novel silicone ceslm uaterlals called glass resin I00 mad glass resin
650 manufactured by Owens-ILllaols were also investigated as coating materials.
Initial studies were carried out at a low pyrolysis temperature, with and with-
out stea_ treatment to determine the effect on electrical measurements. The
results of these studies are listed in Table 35. Several points are obvious
from these studies: (1) steam treatment is necessary to obtain high electrical
resistance a: the lower pyrolysis temperatures, 473 and 573 K, and (2) a
pyrolysis temperature of 573 K is adequate _n generating a coatin_ with high
electrical res4stance, (3) thls coating material appears promising in that an
electrical of about 150C ohms was obtained and appears to be reproducible as
shown by runs SC-22 and 5C-36, (4) the highest electrical resistance was ob-
tained by a 673 K pyrolysis t_perature.
3.6.3.2.1 Fiber Properties
Toe weight percent increase and tensile loads for the glass resin i00 coated
Cellon 6000 are listed in Table 35. Here again, a range in weight percent
coatlugs are generated in these coating studies. A weight ,ncrease of 17.3%
(run SC,-36) would cause an J_crease in fiber diameter of a_out OoS:am. The coated
fiber _rLth the highest electrical resistance, run SC-37, represents 21.4% Ln-
crease in fiber weight, or a diameter Increaae cf O. 75bm. The tensile loads
required to fracture these coated yarn samples (SC-36 and -37) are equivalent
to the load required to fracture "as-recelved" Cellon 6000 yarn. This indicates
that the coating or coating process does not damage the fiber. Coated fiber
from runs S¢-21, -22, -23 smd -24 appeared to have undergone about a 10Z loss
in tensile properties.
3.6.3.3 Glass Resin 650 Coating Studies
Owems-llllnois glass resin material 650 was also evaluated. A series of
runs was made over a temperature r_nge of 473 to 1173 K, The results of this
study are listed in Table 36.
Every condition tested produced a coated fiber with much greater electrical
resistance than uncoated fiber. The run made with steam followed by low tempera-
ture pyrolysis (473 _ produced an electrical resistance equlvalent to runs made
using Owens-Illlnois glass resin 100 (Ii00 to 1500 ohm), However, in contrast with
the high temperature runs with this latter resin, a run made at a pyrolysis tem-
perature of l173Kylelded a coated f_,ber with a resistance of 6500 ohms. This
result shows that both glass resin systems are capable of forming high resistance
ccatlngs on Celion 6000 graphite fibers.
24
3.6.3.3.1 Fiber Properties
table )6 lists the veight percent coating on Celton 6000 fiber generated
by coating vith 81ass ¢esin 650 and the tensile loads required to fracture the
coated yarns. The range of weight increases due to the coating is 17.7 to 30.2Z,
sindlar Co that experienced _'ith glass resin 100 and ethyl silicate. _he In-
crease in coating thickness would be 0.5 to 7._m. Except for yarn samples from
run SC-_7, tensile loads required to fa_l the tensile specimens of coated yarn
are equivalent to that required to fail "as-received" Celion 6000 suggesting
that the coating or coating process does not degrade the tensile strength of
the fiber. Apparently the 1173 K pyrolysis temperature used in run $C-47 pro-
duces a high electrical resistance coating, but causes a 56_ loss in tensile
strength.
3.6,3.4 Tri-n-butylborate Coating Studies
The promising results using Owens-Illinois glass resin 100 to yield silica-
like coated Celion 6000 graphite yarn wlCh a resistance of 1500 ohm suggested
that other statler resin systegs and coating materials should be tested. There-
fore during this program, silica-like coattn 8 studies were discontinued temporarily
to evaluate tr_-n-butylborate as a coating material. ,'he concept behind the use
of tri-n-butylborate is the fact that it is easily hydrolyzed to hydrated boric
acid, and the boric acid is converted to a glassy boron oxide.
3 ÷ a2°3 + 3u. o"beat
A series of runs were Bade at several co_centration levels of trl-n-butylborate
in i_opropyl aZcohol. Table 37 lists the conditions of each run and the re-
sultant resistance of the coated Celion 6000 graphite fibers. It is clear from
the lov resistance _easurements that these concentzatto_ levels of tri-n-butyl-
borate are ineffective in Increasing the electrical resistance of Celton 6000
graphite fibers.
In experca_nts for runs SC-25 through -34, the coated fiber was hydrolyzed
and then returned Into the coating solution. This _as repeated five times be-
fore the final pyrolysls step. In thls approach, it _as found that during _e
amltlple coating operation the boric acid, B(CH)3_ produced in the hydrolys/s
step was being removed in the coating solution. This amant that only the lae¢
coating operation re_uLlted in B(OB)_ pyrolysis to 81easy 320 _. The quantity o_
boron oxide produced on the surface mutt be extrenmly s_ll s_nce the coating
was ineffective in increas_ng the electrical reststmtce of Celion 6000 graphite
fibers.
25
AddlCional rims were made in which the borate ester coated fiber was hydro-
lyzed and subsequently pyrolyzed, followed by another dip into the coating bath.
This process was _epeated five tim. Two runs made from a 2.5 w/o solution did
not produce a boron oxide &lass coating with improved electrlca/ resistance over
the uncoated yarn. Apparently, at this low concentration (2.5 v/o)s even with
five dips, the glass coating produced was extremely thin or is not a coherent
coatlng. Additional studies were noc carried out at higher concentration levels.
3.6.4 Evaluation of Silica-llke Coated Cellon 6000 Graphite Fibers in
Epoxy Composltes
3.6.4.1 Composlte Properties
Composites of the highest resistance coated fibers of each coating material
were fabricated and tested for shear and flexural strength and modulus. Two
hundred feet of coated fiber for each system was required to fabricate 3.75 cm
x 12.5 on x .25 cm composites. The coated fiber was selected on the basis of
high electrical resistance and excellent strength retention of the coated Celion
6000 fiber relative to untreated Cellon 6000 graphite fiber. The resulca of the
mechanical teats are listed in Table 38. The low shear strength values of about
35 KPa (5 ksl) for the coated fibers relatlve to _dmt is usually obtained for
untreated fiber, 115 HPa (15 ksi) clearly damonstrates that each coating saterial
is poorly bonded to the graphite fiber. This is further illustrated by the
poor flexural strength and soduLus values. A typical flexural strength of a
Celion 6000/epoxy composite is 1565 MPa (225 ksi) while these composites ex-
hibited strengths of on/y 279 to 350 NPa (40 to 50 ksi).
A shear failure mode of the flexure1 specimens was noted for each case, a
further indication of the poor bonding of the coating to the fiber. Higher treat-
ment temperatures of the coatings result in loser resistances, but may produce
stronger coatings. Future work should be directed toward obtaining these stronger
coatings.
3.6.5 Conclusions of Organo-Silicone Coating Studi#_
For the organo-silicone coating approach, the best conditions established
as a result of these studies are listed in Table 39 for each mater/al.
26
4.0 GII_PAL COMCLUSIONS
The CVD process for coating graphite yarns vith 51C, 51_ or BN has been
shown to be a method for increasing the electrical resistance of the as-received
yarn. In the case of CVD SiC continuous process with HMS. T-300. Celion 6000 and
Celion 12000 yarns an in-line oxidation furnace could be used to oxidize the sur-
face of the SiC coating to further increase the electrical resistance of the
coated yarn. This ox_dation furnace temperature was varied from 700 to 873 K
_rith either 773 K or 873 K found to be optinum for a particular graphite yarn.
The temperature of the depositfc_ thrasher was also found to be an important
factor in increasing the reactance of the coated yarn with 1398 K an optinu_.
The highest successful drawing rate for the CVD SiC process used was 122 ca/rain
but 30.5 ca/rain was found to be optimum for all five types of graphite yarn
studied in terms of yielding the highest increase £n electrical res4atanCeo It
was found that on the average the CVD SiC continuous coating process with the
in-line oxidation step did not deLrrade the mechanical properties of the untreated
yarn. This was ascertained through hsdividual _ilament testing of ultinate ten-
silt strength.
Small composites were z_de from untreated and CVD SiC coated graphite yarns
£n both PR-2g8 epoxy resins and in UTRC 89-Z resins. The UTRC 89-Z resin con-
tained the components of MY720/DDS. For the untreated and CVD SiC coated yarns
the flexural strength (three point measurement) and short beam shear strength
were lower in the U_fRC 89-Z resin than in the PR-288 epoxy resin for correspundlnB
conditions. All the CVD SiC coated yarns in the UTRC 89-Z resin for the most
part had shear strengths of at least 68.9 }_e (10.0 ksl).
The CVD Si3N_ static coating process was used with HT$, HMS, Celion 6000
and Celion 12000 graphite yarns. An optimum temperature of 1723 K and an zm_ula
to silicon tetrafluoride ratio of 6.01 was found to produce consistently coated
yarn that could withstand 120 VAC open circuit tests without sips of arc_g for
all the graphite yarns stud fed. This _as a static CVD process in _ich
15-20 cm long togs were able to be coated at o_e time. Individual fiber tests
indicated Chat the CUD Si3H _ process dtd not significantly degrade the mechanical
properties of the as-received untreated yarn. The CVD Si3N _ coated H_S graphite
yarn was used to make a coaposite panel with PR-2g8 epoxy resin as the matrix.
_echan_cal tests of these composites were made and the results after correction
for log volume fraction _ere similar to untreated HMS graphite yarn in this
epoxy matrix.
a CVD BN static coating process for both HlqS and Celion 6000 graphics yarns
was £nvestigatad. Deposition temperature of 1873 K for times of I to _$ _nduration were found to produce a BN coating on the _ndiv£dual graphite yarn.
Deposition t4_es of 10 m_n _ere required to produce CVD BN coated yarn which
27
could withstand a 120 VAC arcing test. Ultlmate tensile strength measurements
of uncoated slngle graphite fibers after exposure to the 1873 K thermal environ°
meat showed a considerable decrease in strength. Tests of single CVD BN coated
fibers (after exposure to the 1873 K deposition conditions) save this same low
ulti_te tensile strength. Thls low tensile strength of the CVD BN costed fibers
£_ felt not to be due to the CVD BN process but to the thermal exposure effects
of 1873 K on the graphite yarn.
For the organo-sflfcone coating approach the best conditions established
as a result of these studies produced silica-llke coated Celion 6000 graphite
fibers vlth an electrfcal resistance ranging from 720 to 2950 ohms, compared
with 4.0 ohms for "as rece£ved" Cellon 6000 graphlte fibers.
Composites £abr£cated from these coated fibers exhibited shear strengths
of 33 to 45 MPa (4.80 to 6.59 ksl) and flexural strengths of 261 to 374 HFa
(37.9 to 54.3 k_i). These values are considerably lower than can be derived
from "as received" Celion 6000 graphite fibers, sheer strengths of 102 HPa
(15.0 ksi) and flexure1 strengths of 1530 NPa (225 ksi). The composites teatedin flexure failed in a shear mode. Several reasons can account for these low
shear and flexure values; (1) the pyrolyzed organo-silico_e coatin K layer could
be poorly vetted by the epoxy resin, (2) the coattng could be s mechanicallyweak boundary layer. (3) the coating c:,uld be poorly bonded to the fiber surface.
or (4) a coM_Ination of all three, The physical appearance of the coated fibers
suggest that the coating may be a mechanically veak boumdary layer. In order
to improve the bonding of the sillca-llke coating to the fiber, a nlgh pyrolysls
temperature must be used.
28
5.O REI_INCES
1. Uulted States Department of Commerce Nevs, January 20, 1978.
2. N.,_A "fee.hntcal Memorandum 78652, January 1978.
3. NASA Workshop, Hampton, VA, March 23-24, 1978; Dtcus, D., NASA Technical
Memorandum 78761, Hodif£ed Composite Materials Workshop, July 1978.
4. Galasso, F. S., R. Do Veltri and D. A. Seola, "Study of High Resistance
Inorgsnic Coatings on Graphite Fibers", NASA CR-159078, June 1979.
5. Schtle, R. and G. Rosfca, Rev. Set. ]_nstrum., 38, 1103 (1967).
29
Table 1
l_s_tanca Data for C_DSIC Coat/as IbJns on CeLLon 6000 Yarn
Run
Number
N 714
N 715
N 716
717
N 718
719
N 712
8 713
N 720
N 722
725
N 724
N 723
N 722
Ira-Line
l)r_tng Depoeitiou O_ldat£on
sate ,, , up_cn/_L. K K
15 1398-1453 none
3O
6O
90
122
15
30
6O
9O
122
30
60
90
122
773
873
_stjZanco,
Top ..-----}fiddle Bottou
3.5K 45K 7K
3.0K 10K 125K
750 155 118
450 210 220
300 160 390
280 160 450
360 290 210
200 90 110
55 110 I.SK
220 110 200
80K 4.2/¢ 29K10K I.2K 55K
1.SK 1.Sg 1.SK
1.2K 1.1K 1.4K
1.8K 3.3K 5.8K
1.4K 2.1X 4./d_
230 50 28220 70 55
75 155 300
75 60 400
800 600 4.6K
1.2K 1.OK 7.5K
900 2K 650
I.OK 1o6K 250
200 300 800
3O0 4OO 450
140 16 42
13 17 18
30
Table 2
Resistance Data for CVD SiC Coattn 8 knJ ou T-300 Graphite Yarn
Run
Number
727
N 728
N 729
N 730
N 732
N 733
N 734
N 73.5
N 739
N 738
N 737
N 736
Xn-L£ne
Drawtn 8 Depoat tion OxLdat:Lon Resistance, oh_
Race Temp T,mp _ Top PAddle Botto_cm/m:Ln K g
30 1398-1453 none 400 500 300
900 380 320
6O
9O
122
3O
6O
9O
122
3O
6O
9O
z22
300 280 360
260 200 400
210 90 90
1/40 60 95
62 75 100
62 50 150
773 IX I.SK 400
550 650 4O0
200 350 180
550 130 80
70 65 8675 70 80
50 65 200
68 80 155
873 550 280 6.2K
900 270 3.6K
200 i00 350
140 150 210
60 55 50
58 52 55
30 25 75
50 3O 200
31
Table 3
Resistance Data for CVD SlC Coating _ o_ _-_ Graphite _aru
Run
Number
N781
N777
N778
N779
N780
N782
"_765
N766
N768
N769
N770
_78,3
N773
N774
N775
N776
DrawingRace
cm/mtn
15
30
60
90
122
15
3O
65
60
9O
120
15
30
60
90
120
In-Line
Deposition Oxidation Rests tance, ohms
g g
1398-1453 none
773
873
15 g 15 K 18.5 g
12 K 16 g 17 g
3.8 K 5.4 K 3.5 K
3.2 g 5.2 K 3.8 K
73 220 600
100 20O 650
2.6 3.2 3,03.1 3.0 2.8
2.5 4.4 3.5
2.8 4.1 3,2
15 g 12.5 g 7 K
16.5 g 17.5 g 20 g
925 1.1 490
2.8 K 310 390
45 320 500
35 170 38080 92 170
120 110 160
65 90 3248 70 30
5.5 3.8 3.2
5.5 3,2 3.6
95 170 500115 140 600
1.3 g 4.4 g 2.4 K
1.9 g 3.3 g 3.0 K70 19 40
47 13 37
65 12 2560 15 40
4.6 2.7 2.1
3.5 2.8 2.2
32
Table 4
Ult::l.maCm Temlllm Sl:ramSth _d Modulua llmsul_o £Eon Telt8
on Individual 8£C Coated Cel£m 6000 Gr4q_hiee Yarn
Run
Number
Xn-L£_ Ult£_l:e
DrmrlnS Ox£dacio_ Tetmile
cmlm._ K l_a (kai)
N714
N715N716
N717N718
15.0 none 1899 (276)
30.5 none 1888 (274)
61.0 none 2181 (317)
91.5 none 2474 (359)
122.0 none 2278 (331)
N719N712N713
N720
Iq721
15,0 773 1649 (239)
30.5 773 2333 (339)
61.0 774 2142 (311)
91,5 773 1693 (246)
122.0 773 1736 (252)
N725 30.5
N724 61.0
N723 91.5
N722 122,0
As l_c*d Celton 6000
873
873873873
2670 (387)
1910 (277)1941 (282)2137 (3m)
2626 (382)2477 (359)
_ _)5od,_lus
Ge. (io _ p,l)
200 (29,0)185 (26.9)210 (30.4)202 (29.3)148 (21.5)
172 (25.0)
207 (30.0)194 (28.1)157 (22.8)
188 (27.3)
196 (38.4)161 (23.3)195 (28.4)
156 (22.5)183 (26.6)
173 (25.1)
33 ....
_able 5
Ulciumte Tensile Strength and Modulus Results from Test8 on
Individual CVl) SiC Coated !i_ Graphite Yarn
Run
Number
In-line Ultimate
Drafting Oxidation Tensile
Rate _ St ren gth Modulug ___cm/_l.n K _e (ks1) _ Gee (106 psi)
_781 15N777 30
N778 60N779 90
N780 122
None 1696 (246) 277 (40)1755 (255) 305 (44)2184 (317) 321 (47)2t16 (307) 263 (38)2203 (320) 271 39
N782 15N765 30
N768 60
N769 90
N770 122
773 1901 (276) 283 (41)1999 (290) 278 (40)2205 (320) 309 (45)2077 (301) 270 (39)2262 (328) 281 (41)
N783 15 873
N773 30 1
_774 60N775 90N776 122
2369 (344) 293 (43)
2145 (311) 305 (44)
2164 (314) 350 (51)
2310 (335) 274 (40)
2242 (326) 315 (46)
As _eceivedHES 2164 (314) 287 (42)
34
Table 6
l_s£stm_e Data for CND SiC Coating lk.m on 0-12000 @raphiZe Yarn
Run Dratv£ng I)epos£tiou
Ntmbe___.._r Raze _ Tap
c,mlm:l.n K
N872 30.5 139 8.145 3
N874 30.5 1
S876 30.5
tu-L£na
Oxidation Res_tance, ohms
Tamp Top Mtddl.___e Both__.o_nX
773 IX 1,85K 1.4K
873 1,6K .9K I.4K
none .SK 1.2K .4K
35
Fiber
Condition
Table 7
Ultluate Tensile Strength mid Hodulus Resulls fro= Tests
or_ Individual Filaments from C12000 Graphite _arn
ULtimateOxidation Tensile
_ Temp. _ Stren_ith • |L
K _Pa (ksi) GPa
CVD SiC
coated
CVD SiC
coated
CVD SiC
coated
As _ecelved
C12000
Graphite Yarn
none 2144 (311) 231
773 2355 (342) 229
873 2128 (309) 258
2916 (423) 204
(33.5)
(33.2)
(37.4)
(29.6)
36
Tablm 8
l_nal CVD SiC Coating Coadi_tons Chosen for
Various Graphite Yarns
In-Line
Oxidation UTS Resi sC an ce
Yarn Temp.. K MPa (ksl) ohms
HMS 873 2145 (311) 2720
T-300 773 - - 820
Cellon 6000 773 2353 (539) 1520
Cellon 12000 773 2355 (342) 1400
Reactor tetperat_re : 1598-1423 K
Drawing races: 30 cm/ain
Gas input: 0.110 _/min H2, 0.110 _/mtn CH_, 0.015 _/_n CH_SIHC12
37
o
i g
gm_
V VVV
v
U
0
q
_ AA A
_ V_ V
O_ 0_- 0
A^ ^A ^ AAA
_N_
_N_ I I !
_.AA
AA A
o'qr _
0_0f_N_
00,-_
N_C3
I I I_ZZ
38
0 O_ OD _ ,=4 e-I O0
. . _ • _
Iv
®E_
g
,..4
*,4
0 0 r_ r_ Ch O_ 0 0
0 0 0
e'l ,_
I l
39
Table 11
Qualltatlve Arcing Tests on CVD SI_N_ Coated H."_.c-o_+,_---v ..... Fiber
Run
Number
SN-17
SN-18
SN-19
SN-20
SN-21
SN-22
SN-23
SN-24
CVD Slight Cat.as trophlc
mln
i0 90 V 115 V yes (120 V)
20 105 V no no
i0 80 V _,,5V yes (I00 V)
20 no 105 V no
I0 60 V 95-120 V no
20 no 90 V no
10 no 95 V yes (120 V)
20 no 105 V no
Commen t,s
withstood full voltage
withstood full voltage
withstood full volt,age
wlt,hstood full voltage
withstood full voltage
As-recelved -
yarn
20 v 25 v 45-50 V
4O
S-44S-43S-A2
S-34
S-31
S-35
S-36
S-37
S-38
S-41
$-40S-39
Table 12
Ultimate Tensile StrengCh amd Modulus Resultg from Tegts on
Indivudlal CVD $13N _ Coated _ Graphite Filaments
Ultimate
Depos£C£on Hole Ratio Tensile
Teup , _ _ 1_3/SiF_ StremgchJL/edn t/mtn HPa ks1
1723 0.0196 0.1657 8.45 1989 (289)
1623 0.0196 0.1657 8.45 1638 (238)1523 0.0196 0.1657 8.45 1950 (283)
1723 0.0196 0.1179 6.01 1852 (269)
1623 0.0196 0.1179 6.01 2032 (295)
1523 0.0196 0.1179 6.01 2223 (323)
1723 0.0196 0.0727 3.72 1813 (263)1623 0.0196 0.0727 3.72 2203 (320)
1523 0.0196 0.0727 3.72 1882 (273)
1723 0.0196 0.0379 1.93 1872 (272)
1623 0.0196 0.0379 1.93 1882 (273)
1523 0.0196 0.0379 1.93 2252 (327)
.4m _ce£ved BMS Yarn 2284 (3ii)
29S (43)274 (40)288 (42)
256 (37)358 (52)311 (45)
311 (45)325 (47)318 (46)
287 (42)
366 (53)
378 (55)
3!9 (46)
Deposition time 20 _[n
41
_able 13
St:at:to Experiments CVI) S13N 4 Coated ltNS Yarn
Run
NumberReactor SIP4 NH 3 Hole Ratio
K £/mln Z/mln
Tlme
Inln •
SX 85 1723 O.0196 .1657 8.45 5
SN 88 1723 0.0196 .1657 8.45 10
SN 78 1723 0.0196 .1657 8.45 30
S_ 84 1723 0.0196 .1179 6.01 5
SN 87 1723 0.0196 .1179 6.01 10
SN 72 1723 0.0196 .1179 6.01 30
SN 83 1723 0.0196 .6727 3.71 5
SN 86 1723 0.0196 .0727 3.71 10
SN 80 1723 0.0196 .0727 3.71 3O
42
Run
Number
SN 94
SN 93
SN 92
Ultimata Tenaile Strength and ModuXua keults frma Tests o_
Individual CVD Si3N _ Coated HMS Graphite Yarn
UI t £_tt •
Mole Ratio Deposition Tensile
NH3/SiF_ Time St_ensth
nd.n MPa (ksi)
3.71 1 2219 (307)
3.71 3 2458 (357)
3.71 5 2009 (292)
SN 97
5-_ 96
S_ 95
6.01 1 1539 (223)
6.01 3 1839 (267)
6.01 5 not tested
SN 100
S_ 99
S_ 98
As Received
H14S graphite
yarn
8.45 1 2428 (352)
8.45 3 X649 (239)
8.45 5 2129 (309)
- - 2164 (31_)
_,oduluJ
(i0 p,i)
321 (46.7)
323 (46.8)
324 (47.1)
308 (44.7)
275 (39.9)
m o
286 (t1.5)
324 (36.8)
287 (42)
287 (42)
43
Table 15
Experiments]. Ccmdltlons
CVD St3N _ Coated Celiou 6000 Yarn
J:.un Reactor
Number Temp. _ NH3K E Im:l.n _ImJ.n
5._ 103 1723 .0196 .0727
S': 106 1723 .0196 .0727
S._ 105 1723 .0196 .0727
Mole Ratio
3.71
3.7i
3.71
Time
aln
5
10
3O
S_ 102 1723 .0196 .1179 6.01 5
S_ 108 1723 .0196 .1179 6.01 10
S_ 107 1723 .0196 .1179 6.01 30
SS 101
b'N 110
S._ 109
1723 .0196 .1657 8.45 5
172 3 .0196 .1657 8.45 10
1723 .0196 . 1657 8.45 30
44
RLIn
Number
Tabls
Ult£nete Tens£1e Strensth and Modulus Resulr_ from Tests
on Indtvtdun$ CVD Si3N _ Coated Celiou 6000 YarnDepos£t£on Tenperature 1723 K
Ult£umto
Mole Rac:l.o Deposit£on Tensile
_/S iF 4 Time Sc rength
m£n MPa (ksl)
_dulus
GPa (106psl)
SN 113
SN 114
SN 115
3.71 1 1475 (214)
3.71 3 1889 (274)
3.71 5 noc tested
152 (22.0)
186 (27.2)
s_4 116
SN 117
SN 118
6.01 1 1868 (271)
6.01 ) 1875 (272)
6.01 5 2020 (293)
186 (27.0)
216 (31.4)
176 (25.5)
S_ 119
SN 120
SN 121
As kceived
CeLton 6000
8.45 1 1779 (258)
8.45 3 1496 (217)
8.45 5 not tested
- - 2477 (359)
170 (24.6)
214 (31.0)
173 (25.1)
45
Table 17
CVD BN CoatLn 8 Runs om HI_ Grsphite Yaz'n
BF3/NH 3 Ratio of 0°229
Pare Graphi te Number Depost tiou
Numbe_.____r ¥srn of Tc_$ TemperatureK
BN 1
B,_ 2
BN 3
S_ 4
BN $
BN 6
BN7
BN 8
BN 9
BN 10
BN 11
BN 12
BN 13
H,_ 2 1873
1848
1823
1798
1773
1748
Time
t_l.n
3O
2O
15
10
3O
5
180
3O
46
Tabl_ 18
CVD BN Coattn 8 Runs
Cel£m 6000 Graphite Yaru
Depoettton Tenperature 1873 K
BF3/NIt 3 Ratio of 0.229
N_b • r
of Tows 71_e.me_.mm
sin
BN 14
BH 15
BN 16BN 17
BN19
BN Z0U 21
M 22EN 23
2
2
2
2
222
228
5
1015
30
451
I3
310
47
Fiber
Condi tion
CVD BN
coated
BN-19
CVI) BN
coated
BN- 16
labla 19
Ultimate Tensile Strength mad Modulus Results
from Tests on Ind£vidual Filaments from
CVD BN Costed Celien 6000 Graphite Yarn
Ultimate
Time of Tensile
Strength
._Pa (ksl)
I mln 1186 (I?2)
I0 mln 834 (121)
Modulus
oa (zo_p_i__
163 (23.6)
130 (18.8)
48
Tsble 20
Flexural Properties of UTEC 89-Z Epox 7 ?astn 1
Flexural Properties 2
Specimen
No. Strength Hodulu__a (k,i) cPa ' (1o6p,i)
1 81.7 (11.83 3.15 (0.46)
2 109 (15.S) 3.05 (O._A)
3 96.2 (14.0) 3.18 (0.46)
4 95.6 (13.93 3.52 (0.513
5 76.5 (11.13 3.59 (0.52)
1Cure cycle: 2 hrs @ 398 K+ 2 hrs @ 423 K + 2 hrs @ 448 K
2Four point flex, span-to-depth ratio 20/1
49
Table 21
Short Beam Shear Test Results of Composites
with HTS Graphite Yarn
SpecimenNumber
212-6
Fib•r
Coodi rion
untreated
Shear Stren_t h
_a (ksl)
40.3 (5.95)
36.7 (5.31)
41.9 (6.07)L
39.6 (5.75)
212-7 CVD SiC 73.8 (10.7)
79.4 (11.5)74.9 (10.9)
76.0 (11.0."
212-8 CVD SiC
In-Line
Oxidation
99.4 (14.4)
103 (14.9)
lol (3.4.6)
101 (14.6)
5O
.... _ - " 7 "
Table 22
Cempoette T_t Reeull_
Untreated H_S Graphite Yarn
SpecimenNumber
i •__ ,
T 51
T 52
T 54
T 55
T 56
T 58
T 59
Hercules Values
t!HS/250°1 _ epoxy
l_sinmmlm_mam.
286
286
286
286
288
288
288
Avg
Avg
Avg
Avg
Av8
Av8
Avl
Flexural
strength
_a (_i)
}_dulum
GPi (lO6p.,)
Shear
s trengCh_a (ksl)
1129 (164) 185 (26.8) 66.7 (9.68)
1142 (166) 168 (24.4) 44.2 (6.42)
_17_..._4_ 18_27 (27.1) _1151 (167) 180 (26,1) 59.3 (8.60
11.58 (168)1236 (179)
122__9 (178)1206 (175)
1285 (186)I063 (154)
33191220 (177)
1271 (184)1218 (177)
127_..!1255 (182)
1136 (16.5)
1094 (159)115_../3(167)1131 (164)
1285 (186)
1383 (201)
no_.! (174)1289 (187)
1394 (202)1333 (190)
x3ies1358 (197)
190 (27.5) 66.5 (9.64)
197 (28.5) 68.8 (9.98)
19_./3 _ 67.5 (9.79)193 (28,0) 67.6 (9.80)
194 (28.1) 80.5 (11.7)
199 (28.8) 82.5 (12.0)
19.._6 (28,43 so.o196 (28, 4) 81.3 (11.8)
205 (29.8) 75.2 (10.9)204 (29.6) 76.1 (11.0)
202. (29_2) 75.0203 (29,5) 75.1 (10.9)
166 (24. I) 62.0 (9.0)
166 (24.1) 74,8 (10.8)
16....A4iZldl _165 (24,0) 70.3 (10.2)
193 (27.9) 74.3 (10.8)
193 (28.0) 76.1 (11.0)
18_27_ 79..__90191 (27.7) 76,5 (11,1)
191 27.7
197 28.6
19.!3 2e.o194 (28.1)
81.9 (_.9)81., 4 (11.8)
81.3 (11.8)
1165 (169) 3.82 (26.4) 68.9 (1o.o)
51
• r • r . • .
Table 23
Compos£te Test Results
Untreated HHS Graphlce YarnUTRC 89-Z Resin
in
Specimen
Number
CCVD--6
CCVD- 7
T97
Flexural
Str_gt hH_a (ksi)
Avg
747 (108)
807 (117)
713151 (109)
Avg
478 (69.4)
677 (98.1)
77__3.2641 (93)
783
631
1201
Avg 875
(114)
(91.5)
(174)
(127)
Modulus
165 (24.0)
173 (25.2)
17_._2 (24.9)
170 (24.7)
177 (25.6)
178 <25.8)
171 (24.8)
175 (25.4)
204 (29.6)
192 (27.9)
20.9 (30.4)
202 (29.3)
Shear
Strength
MPa (ksi)
45.6 (6.61)
44.7 (6.48)
44.___ (6.45)44.9 (6.51)
36.7 (5.32)
44.6 (6.46)
39.2 _5.69j)
40.z (5.82)
42.2 (6.12)
40.6 (5.88)41.7 (6.04)
43.0 _6:24)
41.8 (6.07)
52
Z- I " L
TabXe 24
Comp_J:l._:e TeoC RuuXr.8
S:f.C Coated amd Ozl.d:Lzed H_S Graphite Yarn
FlexuwaX
t_a (ksl,)
8hesr
HPa (ks_,)
CCVD-9 o,_RC 749 (109)89-z lool (l_,s)
72__2.kv8 827 (120)
158 (22,9)159 (23. Z)
157 (22.8)
.52.9 (7.67)
51.6 (7.48)
47..__oo.50.5 (7.32)
C_:V'D,-IO UTRC 872 (126)
89-Z 864 (125)
99_!Av8 910 (132)
195 (28.2)
185 (26.8)
187 (27.1)
80.1 (11.6)8o.7 (11.7)65..___1(9.45)75.1 (10.9)
53
Table 25
Composite TestI_ treated Celiom
l_sult;$
6000 Yarn
Sped_en
Number
T 62A
T 0213
T 69
T 63
T 64
TS0
Resin
288
288
288
L'TEC
89-Z
UTRC
89-Z
UTRC
89-Z
Avg
Avg
Avg
Avg
Avg
Avg
Flexural
StrengthMPa (ks!)
1981 (287)1888 (274)
197._0 ._
1944 (282)
1918 (278)
1913 (278)
186_.!41903 (276)
1708 (248)1779 (258)
i62.__!1703 (247)
14i7 (205)1470 (213)
17o__!1530 (222)
2i18 (307)
i917 (278)
216____7(314)2068 (300)
1440 (209)1290 (187)
12221317 (191)
Modulus
GPa (10 6 psi)
133 (19.3)
129 (18.8)
13..._4 (19.4)
132 (i9.2)
i3i (19.0)135 (19.6)
12__8 (18.6)132 (19.1)
i34 (19.5)
130 (i8.7)
132 (19.2)
i48 (21.5)
150 (21.7)
i4._2149 (21.6)
149 (21.6)151 (21.9)
14_2i5o (21.7)
_.A.
Shear
Strength
MPa (ksi)
92.5 (13.8)
88.3 (12.8)
92..___7 (13.4)
9t.7 (13.3)
9,_.0 (13.6)94.2 (13.7)
93.8 (13.6)
98.6 (14.3)
100.6 (14.6)
100.__._6 (14.6)
ioo.o (14.5)
32.5 (4.72)
34.2 (4.97)
39.__/235.4 (5.13)
42.2 (6.12)
48.5 (7.03)
45.1 (6.54)
47.1 (6.83)
52.8 (7.66)
6o.__253.4 (7.74)
54
Table 26
Compos£te Test bsulteCVD SiC Coated amd Oxidized
Celion 6000 Graphite Yarn
T-67A
T-67B
T-70
T-71
T-72
m
UTRC
89-Z
UTRC
89-Z
UTRC
89-Z
UTRC
89-Z
Ave
Avg
Ave
Avg
Avg
Flexural
_a (ksl)
752 (109)
1193 (173)
73,_Z889 (].29)
786 (114)
745 (108)
98.3s/A_827 (120)
696 (lol)814 (118)
95__8szo (1].9)
731 (lo6)924 (134)
862 (125)
758 (110)696 (101)
765 (i].1)
Sheer
_a (lu,l)
138 (19.6)138 (20.1)
132 (19.2)
139 (20.2)136 (19.7)
x2_._5¢,].8.2)132 (19.2)
59.9 (8.69)50.3 (7.29)
88._..256.2 (8.15)
it. 7 (6.05)43.2 (6.26)
43....._442.4 (6.15)
134 (19.4) 102.7 (11.9)
139 (20.2) 104.1 (15.1)
14_.33_ 1;o._.._o06.o)]'39 (20.1) 105.5 (15.3)
]'37 (19.8)130 (78.9)
13_.3e_2o.0,_135 (19.6)
121 (17.5)
12.5 (18.1)
12___s (18.]')124 (17.9)
60.5 (8.77)
:;5.5 (8.05)
86.__2 (8.1_3)56.7 (8.23)
46.7 (6, 78)
45.9 (6.66)
54.__.oo(!-83,)48.9 (7.09)
55
Teble 27
Composite Test Results
T-300 Graphite Yarn
SpecimenNumber
T 73
T 77
T 78
T 84
T 85
Fiber
TreatmentJ
none
none
Qone
C_ SiC/O 2
CVD sic/02
Flexural
Res_ Strength_Pa (ksi)
U'£RC 1303 (187)89-Z 1338 (194)
135_.!AvE 1324 (192)
L_RC 1606 (233)
89-Z 1462 (212)
139__.2(202)1409 (216)Avg
UTRC89-Z
Avg
UTRC
89-Z
Av8
t_RC89-Z
• Avg
1376 (200)1913 (278)
16721654 (24O)
813 (118)
603 (87.5)
724 (105)
7_8 (lO4)541 (78.5)
6O5 (87.8)
621 (90. 1)
Shear
ModulusMPa (ksl)
132 (19.1)130 (18.9)
13_j2132 (19.1)
139 (20.1)
139 (20.2)146 (21.Z)142 (20.5)
143 (19.3)
144 (20.8)
13_8s(_2o;I_)142 (20.0)
119 (17.3)113 (16.4)
12jx (17.6)118 (17.1)
124 (18.0)
115 (16.7)120 (17.4)
120 (17.4)
41.2 (5.98)
29.4 (4.26)
29.__! (7.15)40.0 (5.18)
49.3 (7.15)
48.1 (6.98)
52.950.1 (7.27)
93 (13.5)98 (14.2)62 (9.03)84 (12.2)
97.9 (14.2)
81.3 (11.8)
95._.._._(j3.8)91.7 (13.3)
63.5 (9.20)
66.2 (9.60)
65.6 (9.52)
66..__h.465.4 (9.49)
56
Table 28
Composite Teac Results
Celton 12000 Graphite Yarn
S pe cimen
Number
T 91"
T 95*
T 93
T 94
Fiber
_reatmeuC
none
none
C'_,_ SlC/O 2
_st._._n
PR-288
C_ S_C/O 2 UTRC89-Z
Avg
UI_C
89-Z
ArK
PR-288
Flexural
_a (_i)
N.A.*
N.A.*
1317 ( 191)1425 (2o7)
Avg 1288 (187)
1065 (154)
_1065 (154)
Avs 1142 (165)
. Mod.alusG?a (106ps£)
H.A.*
N.A. *
115 (16.7)116 (16.9)
n__! (17.o)116 (16.9)
136 (19.8)
133 (19.2)
134 (19.6)
Shear
StrenchJr___.',ma(ksl)
106 (15.4)111 (16.1)
112 (16.2)
111 (16.1)110 (16,0)
107 (15.5)
98.6 (14.3)
107 (15.5)
98.__2 (_4.3)103 (14.9)
lOS (15.2)104 (15.0)
lO._! _15.6)lo5 (15.3)
75.1 (10.9)
74.3 (10.8)
69.__473.1 (10.6)
*Specimens failed in compresslon
57
Id
_ °V
i'_ A A
v
A A A
NI• !_ _
_lml|
A
A
N
A A
_ I u'_ ¢'_
,=.4
4J _,,
I,.
O
,...0 O
,.=i
P_ t_
v
P_
v
P_
N
V
,...I
P_
P_,-4
P5P5
OO
&
Q
,,.4v
v
N
,..4
V
O...4
.x
O
01sa
I.,
d_,=..I
|.,=guIV
AJ_a
58
Gra_h£ ta
U_S
U_
U_
HMS
H_
T-300
T-300
_lieu
6OOO
Celien
12OOO
Ce.lton
120O0
Table 3O
Cospo_ims D, livered Co _.,ASA
CV'D
S£C only
Y_
no
yes
PC)
yes
yes
DO
yes
Number
of Yas_els
3
3
3
3
3
3
3
3
3
3
Size
cmm
7.6 x 7.6
7.6 x 7.6
7.6 z 7.6
7.6 z 7.6
7,6 z 7.6
7.6 z 7.6
7.6 x 7.6
7.6 x 7.6
7.6 x 7.6
7.6 z "7.6
UnLdLrectional
Pl£es_lmam
16
16
16
16
16
16
16
16
16
16
59
Table 31
CoaCed lIMS Graphite YarnPR-288 Resin Hatrtx
Composlte
Number
r-88
T-89
T-90
Thickness
c= (in)
.036 (.014)
.056 (.022)
.090 (.038)
Avg
Avg
Avg
Flexural
Strengthl_a (ksi)
713 (103)
486 (70.4)
77_._5 _112)_656 (95.1)
444 (64.3)
484 (70.2)
76_!564 (81.8)
670 (97.2)
627 (90.9)
634 (91.9)
Modulus
G_a (xo_ p_i)
77.1 (11.2)
62.5 (9.1)
13__/_792.4 (13.4)
83.0 (12.0)
86.2 (12.5)
14__4 (2,.o)zo5 (15.2)
119 (17.3)
108 (15.7)
lo__9 (15.8)112 (16.3)
6O
Tsble 32
OrStno-Stltcone Kster_J.s Selected for Ev81_cton
NeChyZtrlethoxysilane (RTS) CH3-SI(OC2Hs) 3
VinyltrlaceCoxysllane (VTS) CH2-CH-St-(00_-CH3) 3
$111cone Resin GE (SR 355)c_3 c_,3
CR3 CH3
Ethyl silicate prepoly_er (ES)_R Silicate Binder #18
2HS/n
61
Table 33
Conclustou8 from Static Tests
Oxlda tlon ks istan ce SEM Tens ile
Results l_sult8 Observa.tlons ' Results
HT5 Poor Good Good -
_qS Poor Good Poor Good
SR 355 Good Good Fair Good
ES Good Good Good Good
62
1_. NO.
_abl.e 34
Propert£u of |thyl 8£1£cace Coated
C_ltm 6000 _raph£ce Yarn
Colt_ C_ditio__l_'Z
Ethyl
Silicate See,-- ?yrolygi,
CoaCinz Temp Tamp
SoluCiou --.L-- K
tiC-11 2.5 393
-12 2.5 nmw
-13 3. $ 393-14 5.0 393-1S 3.5 393
-16 5.0 393
-17 8.0 393-18 10.0 393-19 5.0 393
-20 5.0 393
Ysrn Pronertteot I _ _ mi --
1093-1173
Electrical
Raaiq_tance Wt: g Load 4,5ohm" Coat,us (lbs) (_)
SO-51 2.5 ,',one 473
-48 2.5 393 473-50 2.5 noue 673
-49 2.5 393 573-5& 3.5 none 473
-55 3.5 393 473-53 3.5 none 573
-52 3.5 393 573
4.0 none 143 636
8 m _ w
15 - - -29 - - -27 - - -
36 - - -180 - - -
40 - -75 24.7 126 560
95 35.5 105 467
m o
2950 25.8 138 614
180 19.3 140 623
480 22.3 138 614
190 20.4 123 547
60 34.5 135 601
120 21.0 135 601340 22.5 119 529
1pyrolysis done in N2
2drawing rate 0.91 a/m4n
32.5 c= di_t:ance between electrodes
42.5 ca gage length
5a'veraKe of six specimens
63
table 35
Properties of Glass Resin lO0 Coated Cellon 6000 Graphite Yazn
1,2Coat_K Condl tlons
_t Z
Glass
Resin
100
Coat£ug
_un No, Solution
"As-
received"
5C-41 3.8
SC-37 3.8
S¢-40 3.8
S0-38 3.8
SC-39 3.8
SC,-36 3,8
SC-35 3.8
SO-21 3.8
SC-22 3.8
sc-23 3.8
50-24 3.8
, Yarn Properties
Steam Pyrolysls Electrtcal
Temp Temp. Res£stamce Wt Z
_ ohms 3 CoatinR
4,0 none
none 673 800 25,9
398 673 2900 20,4
none 773 ii00 24,4
398 773 1700 22.7
398 873 800 22.0
398 573 II00 17.3
398 573 230 -
none 573 22 16.2
398 573 1500 46.9
nom 473 30 23.9
398 473 500 12,4
ipyrolyels done in N2
2drawlng rate 0.91 m/mln
32.5 ca distance becueen electrodes
42.5 cm gage length
5averaEe of six speclmens
Yarn
Fracture
Loads4_ 5
143 636
140 623
133 592
139 618
144 641
140 623
143 636
128 574
130 578
121 538
132 587
64
_ Coacinz Condic_ona 1'2 yarn ._roperC!es _wc Z
Glass
Resin Yarn
650 Steam Pyrolysis Electrical Fracture
Coatlns Temp Temp ResleCance WC Z Load_'_'"
• m No,. Solutio__.___n K K . ohms3 Coatinz
- "_- - - 4.0 - 143
zecaived"
SC-42 2.5 no_e 1173 100 17.7 135
SO-44 2.5 398 473 1250 30.2 l/K)
SC.-43 2.5 none 573 720 22.1 140
SC.-_6 2.5 398 773 370 22.5 147
SC--47 2.5 398 1173 6500 19.9 63.1
636
601
623
623
654
281
lpyrolys£s done in N2 atmosphereZdrm_inS race 0.91 m/rain
32.5 cm distance between electrodes
42.5 ca sage lensth
5average of six specimens
65
Table 37
Pyrolyzad tri-n-butyl Borate Coated Celion 6000 Graphite Fibers
Produced by the Modified Ccmttnuous Coating Apparatus
Conc. Py rolysis
Run t rl-n-buty I Dra_ing Steam Temp in Electrical
No._._. B.ora_ e Rate _ _2 Res is tance 1
wt _ re�rain K K ohms
$C-25 2.5 0.91 398 973 6.8
SC-26 2.5 0.91 398 473 5.7
SC-27 2.5 0.91 398 873 6.7
SC-28 2.5 0.91 398 573 5.9
SC-29 2.5 0.91 398 473 5.6
SC-30 2.5 0.91 398 973 3.9
SC-31 5.0 0.91 398 973 6.8
SC-32 10 0.91 398 973 5.4
SC--33 20 O. 91 398 973 5.1
SC.-34 20 0.15 398 973 7.5
1The resistance of a specimen 7.6 cm long, with a 2.54 cm sec_lon free
between the copper block electrodes
66
Table 38
Hechanlcal Properties of Colposltes Contedntn8 Silica-Like
Coated Celion 6000 Graphite Fibers in Epoxy Matrix
Composite Coating Shear
No_ _-terlal Streng_hl
_a (k,-i)
CSC-39
CSC-43
CSC-48
Flexural Properties 2
Strength __ Modulus
)ma (_i) GPa (106
Glass Resin 40.3 (5.85) 261
100 38.3 (5.55) 305
41.3 (5.99) 355
Glass Resin 35.7 (5.18) 262
650 35.7 (5.18) 288
35.1 (5.09) 279
Ethyl 35.7 (5.18) 372Silicate 33.3 (4.83) 374
45.4 (6.59) 374
psi)
(37.9) 65.3 (9.47)(44.3) 66.7 (9.68)(51.4) 77.7 (tl.3)
(38.1) 88.6 (12.9)
(41.8) 80.3 (11.6)(40.5) 84.6 (12.3)
(54.0) 70, 7 (10.2)(54.3) 73.6 (10.7)(54.3) 74.6 (10.8)
1sip- 4/1
2Four point flexure test at a span-to-depth ratio of 20/1
_7
Table 39
Optimum Conditions for Organo-Slllcone Coatln8
of Cellon 6000 Graphlte Fibers
wt _.
Run Coating Coat in 8
No___. Material Solution
"as recelved" none
SC-48 Ethyl Silicate 2.5
gC-38 Glass Resin I00 3.8
£C-43 Glass Resin 650 2.5
Steam Electrical
Temp Pyrolysls Ees is tance
K Temp, .KJ, ohms
- - 4.0
398 573 2950
398 573 ....IIUtl
none 573 _
Yarn Fracture
Loads
143 636
138 614
144 641
_u 623
68
!!
Ik
?g-o;-281-12
TOREACTOR
CONSTANTTEMPWATERBATH
STAINLESSSTEEL TANK
Z:
CARRIER GAS INPl.rl'
SIGHT LEVEL GAGE
Fig. 2 Slime Evaporal_
79--01--273--3
i •
Fig. 3 Graphite Resistance Furnace Used for CVD Si3N 4
76--220 _O-- 4..-119--5
TOPEXHAUSTLINE
GRAPM_'TERRER
ELECIF_DE
NIGHTEMI::_ERL&TUI_EINSULATION
VACUUM VALVE
BOTTOM EXHAUST LINE
IHEATER WINDING
=,\REACTANT GAS _
Fig. 4 Schematic ol I)eposltlon Furmme
80.-4,-119-1
r
t
I
• 1+"
•II-2113-8 I0-+I--+11)-2
!HYDROLYSIS
ZOnE
PYROLYSIS CHAMB_=I
FCR _:]'OH)3 COATING
• - FI31ER FEED
".:, • SP00.
"t
Fig. 6 Modified Continuous Fiber Coating Apparatus
80--130- A 80--4-- 119-4
i-
:E
0
0
0
0>)-Cg
0
o(,-
I-
z_
I,u
iE|
0
79--0_--48-2
|||'3
=_
r.:
i
|(J
6ILL
7g-263- A 80-4--119--3
¢
79--01 -261 -19
:.:i
0
79- I_-,III.- 1
80--4--11g-6
5 MIN
30 MIN
Fig. 12 CVD Silicon Nitdde Coated HTS Graphite Rber
79-02 105 3
45MIN
60MIN
Fig. 13 CVD Silicon Nitrkle Coaled HTS Graphite Fiber
79--0_ .10__2
15 MIN
30MIN
60 MIN
aS_3N4 STANDARD
Fig. 14 X-Ray Diffraction Patterns o! Silicon Nitride Coated HTS Graphite Fiber
.'79--02-1 05--1
PJEPOSITI_)N "EVIP'I_RATUR- 16/3'(
TIM- 5 MINUTES
w
" _L
?
i_._.____lr,_m
Rg. 15 SEM of Silicon Nltrlck CoatExi HTS Graphite Yam
79--04--97-- 1
I
DEPOSITION TEMPERATURE: 1673K
TIME: 10 MINUTES
°
..... _.... -_ _ -----,aim
2#'"
Fill. 16 SEM of Silicon Nitrlde Cooted HTS Graphite Yam
79 -04--97--2
DEPOSITION TEMPERATURE: 16"/3K
TIME: 16 MINUTES
I I
r
Fig. 17' SEM of Silicon Nitride Coaled HTS Graphite Yam
?9-04--97--3
DEPOSITIONTEMPERATURE:1593KTIME:SMINUTES
,q
Fig. 18 SEM of Silk:on Nitride Coated HTS Graphite Yam
79--O4.-- g7--dl
DEPOSITION TEMPERATURE: 1593K
TIME: 10 MINUTES
Fig. 19 SEM of Silicon Nitride Coaled HTS Graphite Yam
?9-04--9?-5
DEPOSITIONTEMPERATURE:1583KTIME:15MINUTES
l
Fig. 20 SEM of Silicon Nitride Coated HTS Graphite Yam
?9-04- 97-6
|
Fig. 21 SEM of "As Received" HT$ Graphite Fiber
19-04--97-7
5 M'N _q'lF I_EPCSIIIO%
NH3/SiF 4 = 3.71 20/Jm NH3/SiF4 = 6.01 20_m
Fig. 22 CVO Si3N 4 Coated HMS Yarn
79--09- 35-- 1
"C Mh'_UTE DEPOSITION
NH3_iF 4 = 3.71t.---..-J2Opm NH3_tF4 =,, 6.01 _3pm
NH3PSiF4 = 8.45 23_ ,-r,
Fig. 23 CVD Si3N 4 Coated HMS Yarn
79- .%)- 35--2
30U'NUIECEPCSII"IOK
NH3/SiF 4 == 3.71 NH3#SiF4 = 6.01
NH3/SiF 4 = 8.4520u-
Fig. 24 CVD Si3N 4 Coaled HMS Yam
79- O9--35--3
HMS GRAPHITE YARN
LOG,A'ION WITHIN COMPOSITE
END OF TOW NOTINCLUDED IN COMPOSITE
TOP REGION
MIDDLE REGION BOTTOM REGION
Fig. 25 CVD Si3N 4 Coatings
80.- 3-- lS)- 1
5 MINUTE D_POSITION
NH3t_F 4 - 3.71
" p,u
I.-.--..-I'0 ;1 NH,_'_F4"_,, 6.01 :Opm
NH3/SiF 4 " 8.45 I I13_-.
Fig. 26 CVD Si3N 4 Coated Cglion 6000 Yarn
79-09-1,50- 3
Inh 4_4_ _irh_ I 1_/_7/q_ I_?_TAM "
1:) &'INUTE DEoc)sCrlC_
NH3_iF 4 "_3.71 NH3/5iF 4" 6.01
NH3_F 4 = 8.45 t •lO_rn
Fig. 27 CVD Si3N 4 Coaled Celion 6000 Yam
79-O9-- ! 50-2
UINI.J'T'EDE_"t'tC_N
NFI3JSiF 4 = 3.71 _ NH3/SiF 4 6.0'!1C1/m "
NH3/SiF 4 " 8.45 l.--.____J"13p'n
Fig. 28 CVD Si3N 4 Coated Cellon 6000 Yam
_9-09-150-1
C12000 GRAPHITE YARN
Fig. 29 CVD Si3N 4 Coatings
23 k'..tJUTES
80--1--167--1
CEL_ON E03C GRAPHI T=. YARN
1 MINUTE DEPOSITION
10 MINUTE DEPOSITION
Fig. 30 CVD BN Coalings
80-3--19-2
CELION60:30GRAPHIT:..YA_N
30 MINUTE DEPOSITION
45 MINUTE DEPOSITION_ljm
Fig. 31 CVD BN Coetings
Imo-)-- 19-3
aASA [ ........ i , , i
4. Tree me Ik_t_e ......
COAZINGSFOR..... , ,,=, - • nmumn nlm n I I : -- --
7, A,Jthor(s}
F. S. Galasso, _. Ao Scala and R. D, Veltr£
i • ill I
O. PWfor_i,'_l_pnizat_ Na_ _ Addrm
Uuited Te_nolo&ieo Corporation
b_tted Technolodiu P_meearch Center
East: _arc£ord, CT 06108
12. Spo_I_ _ler_y Na_ and _Idras
National A_ornautico and Space A_zinistration
WashinGton, DC 20546• i Lll i
t& _p_rv Nora
as Pelonniq O_int_ Aq_1 No.
R80-914212-22m
10. Work Umt No
_!i. Co_rlcl or Grant NO.
NA51-14346
13. Type of Repo_ i_d l_rx)d Co,,wed
Coutractor Bepor_
Contrac_ _o_ito_' Dennis Dicue, NASA Landtey _eoarch Center
16........ n _ • I I • m .......
JId_ua(:t
It vim reported that 8raphi_e fibers _eloue_ from composiCee durin8 bu_nK or an
explosion could _auoe ehortin8 of olec_rical and el_ctrouic equipme_t. In _his pro-
&rl, silicon carbide, silica, silico_ mint-Ida end boron nitride were coated on
iraph£te f_be_ to increue their elsc_rtcaZ rulst_ces. A chemical vapor deposited
s£1£co= ca_oLde fo_l_d by an oxidation process developed _or XTS fiber was used
to coat _MS, C-6000, C-12000 and _-300 |raphi_e _bero _eois_ences as hidh as three
orders of upi_ude hiiher _han uncoated f_ber were attained without shy si_iflcant
desradation of _he substrata fiber. 611Lcon nitrtde and boron nLtride _.oated gibers
have res£stmc_ $reeter _hen 10 G oh_/c_. An organs-silicone approach Co produce
coated ££bers _r£_h hidh electrical resistance was _lso used. Celion 6000 8raphite
fibers were coated rich an orsano-silicone compound, folloved by hydrolysis and
pyrolysis o_ the coat,n8 to a silica-like materi_l. Although a lc_ pyrolysis tem-
perature (57_ I{) resulted in larse increase in elect_ical resistance (2950 ohms),
relative to coated fibers pyrolyzed at 1093 K (18 ohms), the shear and flexural
strengths of composites made from htsh electrically resistant fibers were con-
siderably lower than _he shear and flexural strengths o£ composites made frown the
lower electricall_ resistant fibers. The lower shear strengths of the composites
indicated _ha_ the coatings on these fibers were weaker than the coating on the
££bers which _ere pyrolyzed at higher temperature.
17. Key W_rm (SugJlm_e_ by Autlx)r|t)|
Organosilane coa_ing, Chemical vapor
depos£tion, Sillca-llke coatings, Silicon
carbide coat:Lug, Composites, Graphite
£iber, Silicon nitridecoatiu$, Boronnitride_
ql
I9. Security O_f. (oftg_s report} / 20. Sec_riw C_f. (of this pqel
_nclaset_led _• Unclassified
18, D_il_ticn $_
1_c1_ssif ied-_nllmi_ed
m_
21. No.of Pages 22. Pr_:_"
99-
For sale b_'theNali_)iTechr;;_: '"~-";^" (....... '_..... ' .... .,_,_/
| ........